feat: add Scheduler provider + multi-provider UX fixes

Scheduler provider:
- Virtual provider (no external service) that emits SCHEDULED_MESSAGE
  events on user-defined intervals or cron expressions
- Custom variables stored in tracker filters, flattened into template context
- fire_count persists across triggers via tracker state
- APScheduler CronTrigger support for cron-mode schedules
- Default templates (EN+RU), seeded on startup

Multi-provider UX fixes:
- Tracking config hides Immich-specific sections (periodic, scheduled,
  memory, asset display) for non-Immich providers
- Command config driven by provider capabilities — hides commands/settings
  for providers without bot commands
- Template config hides empty "Scheduled Messages" group
- Test menu on tracker targets is provider-aware (Immich shows all 4 test
  types, others show only basic)
- Removed redundant Test button from tracker card
- System-owned tracking configs (user_id=0) seeded for Gitea + Scheduler
- Fixed ownership checks to allow system configs in tracker-target links
- Capabilities cache shared across template-configs and command-configs
- Command tracker bot selector uses EntitySelect instead of raw select
- Sample context includes Gitea + Scheduler variables for template preview

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

@@ -2,7 +2,7 @@
 	import { onMount } from 'svelte';
 	import { api } from '$lib/api';
 	import { t } from '$lib/i18n';
-	import { commandConfigsCache, commandTemplateConfigsCache } from '$lib/stores/caches.svelte';
+	import { commandConfigsCache, commandTemplateConfigsCache, capabilitiesCache } from '$lib/stores/caches.svelte';
 	import PageHeader from '$lib/components/PageHeader.svelte';
 	import Card from '$lib/components/Card.svelte';
 	import Loading from '$lib/components/Loading.svelte';
@@ -37,22 +37,23 @@
 	let submitting = $state(false);
 	let confirmDelete = $state<any>(null);
 
-	const allCommands = [
-		{ key: 'help', icon: 'mdiHelpCircle' },
-		{ key: 'status', icon: 'mdiChartBox' },
-		{ key: 'albums', icon: 'mdiImageMultiple' },
-		{ key: 'events', icon: 'mdiPulse' },
-		{ key: 'summary', icon: 'mdiFileDocumentEdit' },
-		{ key: 'latest', icon: 'mdiImagePlus' },
-		{ key: 'memory', icon: 'mdiHistory' },
-		{ key: 'random', icon: 'mdiDice3' },
-		{ key: 'search', icon: 'mdiMagnify' },
-		{ key: 'find', icon: 'mdiFileSearch' },
-		{ key: 'person', icon: 'mdiAccount' },
-		{ key: 'place', icon: 'mdiMapMarker' },
-		{ key: 'favorites', icon: 'mdiStar' },
-		{ key: 'people', icon: 'mdiAccountGroup' },
-	];
+	// Immich command icons — used as fallback when capabilities don't specify icons
+	const commandIcons: Record<string, string> = {
+		help: 'mdiHelpCircle', status: 'mdiChartBox', albums: 'mdiImageMultiple',
+		events: 'mdiPulse', summary: 'mdiFileDocumentEdit', latest: 'mdiImagePlus',
+		memory: 'mdiHistory', random: 'mdiDice3', search: 'mdiMagnify',
+		find: 'mdiFileSearch', person: 'mdiAccount', place: 'mdiMapMarker',
+		favorites: 'mdiStar', people: 'mdiAccountGroup',
+	};
+
+	let allCapabilities = $derived(capabilitiesCache.items);
+	let providerCommands = $derived<{key: string, icon: string}[]>(
+		(allCapabilities[form.provider_type]?.commands || []).map((c: any) => ({
+			key: c.name,
+			icon: commandIcons[c.name] || 'mdiConsole',
+		}))
+	);
+	let hasCommands = $derived(providerCommands.length > 0);
 
 	const defaultForm = () => ({
 		name: '',
@@ -72,6 +73,7 @@
 			await Promise.all([
 				commandConfigsCache.fetch(true),
 				commandTemplateConfigsCache.fetch(),
+				capabilitiesCache.fetch(),
 			]);
 		} catch (err: any) { error = err.message || t('common.loadError'); snackError(error); }
 		finally { loaded = true; highlightFromUrl(); }
@@ -170,11 +172,12 @@
 				{/if}
 			</div>
 
+			{#if hasCommands}
 			<!-- Enabled commands -->
 			<div>
 				<p class="text-sm font-medium mb-2">{t('commandConfig.enabledCommands')}</p>
 				<div class="grid grid-cols-2 sm:grid-cols-3 md:grid-cols-4 gap-1">
-					{#each allCommands as cmd}
+					{#each providerCommands as cmd}
 						<label class="flex items-center gap-1.5 text-xs cursor-pointer hover:bg-[var(--color-muted)] px-2 py-1 rounded">
 							<input type="checkbox" checked={form.enabled_commands.includes(cmd.key)}
 								onchange={() => toggleCmd(cmd.key)} />
@@ -212,6 +215,11 @@
 				<input type="number" bind:value={form.rate_limits.default} min="0" max="300"
 					class="w-full px-2 py-1.5 text-sm border border-[var(--color-border)] rounded-md bg-[var(--color-background)]" />
 			</div>
+			{:else}
+			<div class="text-sm text-[var(--color-muted-foreground)] p-3 border border-[var(--color-border)] rounded-md">
+				{t('commandConfig.noCommandsForProvider')}
+			</div>
+			{/if}
 
 			<button type="submit" disabled={submitting}
 				class="px-4 py-2 bg-[var(--color-primary)] text-[var(--color-primary-foreground)] rounded-md text-sm font-medium hover:opacity-90 disabled:opacity-50">