feat(immich): per-album scheduled/memory dispatch + template tooling

Dispatch: honor {kind}_collection_mode on TrackingConfig — "per_collection"
fans out one event per album; "combined" pools assets as before. Extract
build_immich_dispatch_events shared by cron and test paths.

Assets: collect_scheduled_assets attaches album_name/album_url/album_public_url
to each asset so combined-mode templates can attribute rows to their source
album. Default scheduled_assets templates render a multi-album header with
inline album list and per-row album link; memory_mode follows the same pattern.

UI: "Reset to default" buttons on notification and command template slots
(per-slot and whole-template), backed by new GET /*-template-configs/defaults
endpoints. tracking-configs "Preview template" now opens an inline preview
modal with locale tabs instead of navigating away; Edit button deep-links
with ?edit_slot=<name> so the destination auto-opens the config and scrolls
to the slot. Reset confirmations use ConfirmModal instead of window.confirm.

Fixes:
* NotificationDispatcher._session_ctx infinite recursion when no shared
  aiohttp.ClientSession was passed — broke test dispatch for periodic/
  scheduled/memory (cron path was unaffected).
* telegram-bots /chats/{id}/test now resolves chat.language_override /
  language_code instead of using the raw ?locale query param, matching
  the resolution the tracker-target test endpoint already used.
* scheduled_assets default template no longer emits a blank line between
  header and the first asset when the multi-album branch is taken.

frontend/src/routes/tracking-configs/+page.svelte

@@ -12,6 +12,9 @@
 	import MdiIcon from '$lib/components/MdiIcon.svelte';
 	import EmptyState from '$lib/components/EmptyState.svelte';
 	import ConfirmModal from '$lib/components/ConfirmModal.svelte';
+	import Modal from '$lib/components/Modal.svelte';
+	import { sanitizePreview } from '$lib/sanitize';
+	import { supportedLocalesCache } from '$lib/stores/caches.svelte';
 	import Hint from '$lib/components/Hint.svelte';
 	import IconButton from '$lib/components/IconButton.svelte';
 	import IconGridSelect from '$lib/components/IconGridSelect.svelte';
@@ -22,13 +25,150 @@
 	import { getDescriptor, buildTrackingFormDefaults } from '$lib/providers';
 	import ErrorBanner from '$lib/components/ErrorBanner.svelte';
 	import Button from '$lib/components/Button.svelte';
-	import type { TrackingConfig } from '$lib/types';
 
 	/** Grid-select item source lookup — maps descriptor string name to actual function. */
 	const gridItemSources: Record<string, () => any[]> = {
 		sortByItems, sortOrderItems, albumModeItems, assetTypeItems, memorySourceItems,
 	};
 
+	/**
+	 * HH:MM, comma-separated: "09:00" or "09:00, 18:30" — the only format cron
+	 * dispatch accepts. Matched on blur for time-list fields; invalid values
+	 * are surfaced inline next to the input.
+	 */
+	const TIME_LIST_RE = /^\s*(?:[01]\d|2[0-3]):[0-5]\d(?:\s*,\s*(?:[01]\d|2[0-3]):[0-5]\d)*\s*$/;
+
+	/** Per-field error messages surfaced inline under time-list inputs. */
+	let timeListErrors = $state<Record<string, string>>({});
+
+	/** Normalize "9:0 , 18:30" → "09:00,18:30" on blur, clear error when valid. */
+	function normalizeTimeList(key: string) {
+		const raw = String(form[key] ?? '').trim();
+		if (!raw) { timeListErrors = { ...timeListErrors, [key]: '' }; return; }
+		if (!TIME_LIST_RE.test(raw)) {
+			// Try a lenient normalization: split on commas, zero-pad each part.
+			const parts = raw.split(',').map(p => p.trim()).filter(Boolean);
+			const fixed: string[] = [];
+			let ok = true;
+			for (const p of parts) {
+				const m = /^(\d{1,2}):(\d{1,2})$/.exec(p);
+				if (!m) { ok = false; break; }
+				const hh = Number(m[1]);
+				const mm = Number(m[2]);
+				if (!Number.isFinite(hh) || !Number.isFinite(mm) || hh < 0 || hh > 23 || mm < 0 || mm > 59) { ok = false; break; }
+				fixed.push(`${String(hh).padStart(2, '0')}:${String(mm).padStart(2, '0')}`);
+			}
+			if (ok) {
+				form[key] = fixed.join(',');
+				timeListErrors = { ...timeListErrors, [key]: '' };
+				return;
+			}
+			timeListErrors = { ...timeListErrors, [key]: t('trackingConfig.invalidTimeList') };
+			return;
+		}
+		// Canonicalise spacing.
+		form[key] = raw.split(',').map(s => s.trim()).join(',');
+		timeListErrors = { ...timeListErrors, [key]: '' };
+	}
+
+	/**
+	 * Quiet-hours preview: "22:00 → 07:00 next day (9h)" or "Quiet period is 0
+	 * minutes — adjust times" when start equals end. Handles overnight ranges
+	 * (start > end) correctly.
+	 */
+	function quietHoursPreview(start: string, end: string): string {
+		if (!start || !end) return '';
+		const [sh, sm] = start.split(':').map(Number);
+		const [eh, em] = end.split(':').map(Number);
+		if (![sh, sm, eh, em].every(Number.isFinite)) return '';
+		const sMin = sh * 60 + sm;
+		const eMin = eh * 60 + em;
+		if (sMin === eMin) return t('trackingConfig.quietHoursZero');
+		const overnight = sMin > eMin;
+		const span = overnight ? (24 * 60 - sMin) + eMin : eMin - sMin;
+		const h = Math.floor(span / 60);
+		const m = span % 60;
+		const dur = m === 0 ? `${h}h` : `${h}h ${m}m`;
+		const arrow = overnight
+			? `${start} → ${end} ${t('trackingConfig.nextDay')}`
+			: `${start} → ${end}`;
+		return `${arrow} (${dur})`;
+	}
+
+	function gotoTemplateConfig(slotName: string) {
+		// Deep-link to the template configs page: pass the slot as a query
+		// param (``edit_slot``) so the destination can auto-open the first
+		// matching config in edit mode and expand that slot. Plain hashes
+		// like ``#slot-X`` were a no-op because slots don't exist in the DOM
+		// until a config is being edited.
+		const u = new URL('/template-configs', window.location.origin);
+		u.searchParams.set('provider', 'immich');
+		u.searchParams.set('edit_slot', slotName);
+		window.location.href = u.toString();
+	}
+
+	/**
+	 * Inline preview of the shipped default template for a scheduled/periodic/
+	 * memory slot. Using the shipped default (not a tracker's current template)
+	 * keeps this scoped to the tracking-config page — which has no concept of
+	 * which TemplateConfig a given tracker uses. Users who want to edit the
+	 * actual config can click "Edit template" in the modal footer.
+	 *
+	 * ``previewLocale`` is modal-scoped so switching tabs only refetches for
+	 * this preview — the user's UI locale (and other previews) are untouched.
+	 */
+	let previewModal = $state<{ slotName: string; rendered: string; error: string; locale: string } | null>(null);
+	let previewLoading = $state(false);
+	let previewLocales = $derived(supportedLocalesCache.items);
+
+	async function openTemplatePreview(slotName: string) {
+		await supportedLocalesCache.fetch();
+		const initialLocale = previewLocales.includes('en') ? 'en' : (previewLocales[0] || 'en');
+		await renderPreviewFor(slotName, initialLocale);
+	}
+
+	async function renderPreviewFor(slotName: string, locale: string) {
+		previewLoading = true;
+		try {
+			const defaults = await api<Record<string, Record<string, string>>>(
+				`/template-configs/defaults?provider_type=immich&slot_name=${encodeURIComponent(slotName)}&locale=${encodeURIComponent(locale)}`,
+			);
+			const template = defaults?.[slotName]?.[locale];
+			if (!template) {
+				previewModal = { slotName, rendered: '', error: t('templateConfig.resetNoDefault'), locale };
+				return;
+			}
+			const res = await api<{ rendered?: string; error?: string }>(
+				'/template-configs/preview-raw',
+				{
+					method: 'POST',
+					body: JSON.stringify({
+						template,
+						target_type: 'telegram',
+						date_format: '%d.%m.%Y, %H:%M UTC',
+						date_only_format: '%d.%m.%Y',
+					}),
+				},
+			);
+			previewModal = {
+				slotName,
+				rendered: res?.rendered || '',
+				error: res?.error || '',
+				locale,
+			};
+		} catch (err: any) {
+			previewModal = { slotName, rendered: '', error: err.message, locale };
+		} finally {
+			previewLoading = false;
+		}
+	}
+
+	const SLOT_FOR_SECTION: Record<string, string> = {
+		periodic: 'periodic_summary_message',
+		scheduled: 'scheduled_assets_message',
+		memory: 'memory_mode_message',
+	};
+
 	let allConfigs = $derived(trackingConfigsCache.items);
 	let filterText = $state('');
 	let filterType = $state('');
@@ -161,10 +301,20 @@
 				{t(section.legend)}
 				{#if section.legendHint}<Hint text={t(section.legendHint)} />{/if}
 			</legend>
-			<label class="flex items-center gap-2 text-sm mt-1">
-				<input type="checkbox" bind:checked={form[section.enabledField]} />
-				{t('trackingConfig.enabled')}
-			</label>
+			<div class="flex items-center justify-between mt-1">
+				<label class="flex items-center gap-2 text-sm">
+					<input type="checkbox" bind:checked={form[section.enabledField]} />
+					{t('trackingConfig.enabled')}
+				</label>
+				{#if SLOT_FOR_SECTION[section.key]}
+					<button type="button" onclick={() => openTemplatePreview(SLOT_FOR_SECTION[section.key])}
+						class="text-xs text-[var(--color-primary)] hover:underline inline-flex items-center gap-1"
+						disabled={previewLoading}>
+						<MdiIcon name="mdiEyeOutline" size={14} />
+						{t('trackingConfig.previewTemplate')}
+					</button>
+				{/if}
+			</div>
 			{#if form[section.enabledField]}
 			<div class="grid grid-cols-3 gap-3 mt-3">
 				{#each section.fields as field (field.key)}
@@ -181,17 +331,32 @@
 						{:else if field.type === 'grid-select' && field.gridItems}
 							<IconGridSelect items={gridItemSources[field.gridItems]()} bind:value={form[field.key]} columns={field.gridColumns ?? 2} compact />
 						{:else}
-							<input type={field.key.includes('date') ? 'date'
-									: field.key.startsWith('quiet_hours_') ? 'time'
-									: field.key.includes('times') ? 'text'
-									: 'number'}
+							{@const inputType = field.type === 'date' ? 'date'
+								: field.type === 'time' ? 'time'
+								: field.type === 'time-list' ? 'text'
+								: 'number'}
+							{@const hasError = field.type === 'time-list' && !!timeListErrors[field.key]}
+							<input type={inputType}
 								bind:value={form[field.key]} min={field.min} max={field.max}
-								placeholder={field.key.includes('times') || field.key.startsWith('quiet_hours_') ? String(field.defaultValue ?? '') : ''}
-								class="w-full px-2 py-1 border border-[var(--color-border)] rounded-md text-sm bg-[var(--color-background)]" />
+								onblur={field.type === 'time-list' && field.validateFormat ? () => normalizeTimeList(field.key) : undefined}
+								placeholder={field.type === 'time-list' || field.type === 'time' ? String(typeof field.defaultValue === 'function' ? field.defaultValue() : (field.defaultValue ?? '')) : ''}
+								class="w-full px-2 py-1 border rounded-md text-sm bg-[var(--color-background)] {hasError ? 'border-[var(--color-error-fg)]' : 'border-[var(--color-border)]'}" />
+							{#if field.inlineHelp}
+								<p class="text-[10px] mt-0.5" style="color: var(--color-muted-foreground);">{t(field.inlineHelp)}</p>
+							{/if}
+							{#if hasError}
+								<p class="text-[10px] mt-0.5" style="color: var(--color-error-fg);">{timeListErrors[field.key]}</p>
+							{/if}
 						{/if}
 					</div>
 				{/each}
 			</div>
+			{#if section.key === 'quietHours' && form.quiet_hours_start && form.quiet_hours_end}
+				<p class="text-xs mt-2" style="color: var(--color-muted-foreground);">
+					<MdiIcon name="mdiWeatherNight" size={12} />
+					{quietHoursPreview(String(form.quiet_hours_start), String(form.quiet_hours_end))}
+				</p>
+			{/if}
 			{/if}
 		</fieldset>
 		{/each}
@@ -268,7 +433,63 @@
 
 <BlockedByModal open={!!blockedBy} detail={blockedBy} onclose={() => blockedBy = null} />
 
+<Modal open={previewModal !== null}
+	title={previewModal ? `${t('trackingConfig.previewTemplate')} — ${previewModal.slotName}` : ''}
+	onclose={() => previewModal = null}>
+	{#if previewModal}
+		{#if previewLocales.length > 1}
+			<div class="flex gap-1 mb-3 border-b border-[var(--color-border)]">
+				{#each previewLocales as loc}
+					<button type="button"
+						onclick={() => renderPreviewFor(previewModal!.slotName, loc)}
+						disabled={previewLoading}
+						class="px-3 py-1.5 text-xs font-medium rounded-t-md transition-colors {previewModal.locale === loc ? 'bg-[var(--color-primary)] text-[var(--color-primary-foreground)]' : 'text-[var(--color-muted-foreground)] hover:bg-[var(--color-muted)]'} disabled:opacity-50">
+						{loc.toUpperCase()}
+					</button>
+				{/each}
+			</div>
+		{/if}
+		<p class="text-xs mb-3" style="color: var(--color-muted-foreground);">
+			{t('trackingConfig.previewSampleNote')}
+		</p>
+		<!-- Keep the prior rendered/error box mounted while refetching on locale
+		     switch — just dim it. Unmounting and replacing with a small "…"
+		     placeholder caused a one-frame layout jump as the modal shrank and
+		     then re-expanded. -->
+		<div class="relative mb-3" style="opacity: {previewLoading ? 0.5 : 1}; transition: opacity 0.15s ease;">
+			{#if previewModal.error}
+				<div class="p-3 rounded text-xs" style="background: var(--color-error-bg); color: var(--color-error-fg);">
+					{previewModal.error}
+				</div>
+			{:else if previewModal.rendered}
+				<div class="p-3 bg-[var(--color-muted)] rounded text-sm preview-html">
+					<pre class="whitespace-pre-wrap text-xs">{@html sanitizePreview(previewModal.rendered)}</pre>
+				</div>
+			{:else}
+				<div class="p-3 text-xs" style="color: var(--color-muted-foreground);">…</div>
+			{/if}
+		</div>
+		<div class="flex gap-2 justify-end mt-3">
+			<button type="button" onclick={() => { const s = previewModal!.slotName; previewModal = null; gotoTemplateConfig(s); }}
+				class="text-xs px-3 py-1.5 rounded-md border border-[var(--color-border)] hover:bg-[var(--color-muted)]">
+				{t('trackingConfig.editTemplate')}
+			</button>
+			<button type="button" onclick={() => previewModal = null}
+				class="text-xs px-3 py-1.5 rounded-md bg-[var(--color-primary)] text-[var(--color-primary-foreground)]">
+				{t('common.close')}
+			</button>
+		</div>
+	{/if}
+</Modal>
+
 <style>
+	:global(.preview-html a) {
+		color: var(--color-primary);
+		text-decoration: underline;
+	}
+	:global(.preview-html a:hover) {
+		opacity: 0.8;
+	}
 	.toggle-switch {
 		position: relative;
 		display: inline-flex;