fix: comprehensive API/UI review — 26 bug fixes and improvements

Backend:
- Scheduler lifecycle sync: create/update/delete tracker now syncs APScheduler jobs
- Test-periodic/test-memory endpoints render actual Jinja2 templates with sample data
- Cascade cleanup on tracker delete (TrackerState removed, EventLog nullified)
- Fix user_id=0 FK violation for system-owned TemplateConfig (removed FK constraint)
- Fix API key leak: only attach x-api-key header for internal provider URLs
- Validate config ownership in tracker_targets create/update
- Fix _response() double-emit of created_at in template/tracking configs
- Add per-target-link test endpoints (test, test-periodic, test-memory)

Frontend:
- Fix orphaned provider on test exception in providers/new
- Add submitting guard + disabled state to targets save button
- Move test buttons from tracker card to per-target-link rows
- Fix Svelte 5 async $state reactivity (spread reassignment for all Record mutations)
- i18n for dashboard timeAgo and event type badges (EN + RU)
- Add required attribute to chat select dropdown in targets
- Fix font CSS vars to prioritize imported DM Sans / JetBrains Mono
- Standardize empty states with centered icon + text across all 6 list pages
- Add stagger-children animation class to all list containers
- Fix slide transition duration consistency (200ms everywhere)
- Standardize border-radius to rounded-md across all form inputs
- Fix providers/new page structure (h2 + mb-8 spacing)
- Fix tracker card action row overflow (flex-wrap justify-end)
- JinjaEditor dark mode reactivity (recreate editor on theme change)
- Add aria-labels to mobile nav items
- Make ConfirmModal confirm button label/icon configurable
- Remove double error reporting on providers page
- Add telegram bot edit functionality (name editing via PUT)
- i18n for External Domain label on provider forms

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/routes/+page.svelte

@@ -31,17 +31,7 @@
 
 	onMount(async () => {
 		try {
-			const [providers, trackers, targets] = await Promise.all([
-				api<any[]>('/providers'),
-				api<any[]>('/trackers'),
-				api<any[]>('/targets'),
-			]);
-			status = {
-				providers: providers.length,
-				trackers: { active: trackers.filter((t: any) => t.enabled).length, total: trackers.length },
-				targets: targets.length,
-				recent_events: [],
-			};
+			status = await api<any>('/status');
 			setTimeout(() => {
 				animateCount(0, status.providers, (v) => displayProviders = v);
 				animateCount(0, status.trackers.active, (v) => displayActive = v);
@@ -64,13 +54,21 @@
 	function timeAgo(dateStr: string): string {
 		const diff = Date.now() - new Date(dateStr).getTime();
 		const mins = Math.floor(diff / 60000);
-		if (mins < 1) return 'just now';
-		if (mins < 60) return `${mins}m ago`;
+		if (mins < 1) return t('dashboard.justNow');
+		if (mins < 60) return t('dashboard.minutesAgo').replace('{n}', String(mins));
 		const hours = Math.floor(mins / 60);
-		if (hours < 24) return `${hours}h ago`;
-		return `${Math.floor(hours / 24)}d ago`;
+		if (hours < 24) return t('dashboard.hoursAgo').replace('{n}', String(hours));
+		return t('dashboard.daysAgo').replace('{n}', String(Math.floor(hours / 24)));
 	}
 
+	const eventLabels: Record<string, string> = {
+		assets_added: 'dashboard.assetsAdded',
+		assets_removed: 'dashboard.assetsRemoved',
+		collection_renamed: 'dashboard.collectionRenamed',
+		collection_deleted: 'dashboard.collectionDeleted',
+		sharing_changed: 'dashboard.sharingChanged',
+	};
+
 	const eventIcons: Record<string, string> = {
 		assets_added: 'mdiImagePlus', assets_removed: 'mdiImageMinus',
 		collection_renamed: 'mdiRename', collection_deleted: 'mdiDeleteAlert', sharing_changed: 'mdiShareVariant',
@@ -137,7 +135,7 @@
 									<MdiIcon name={eventIcons[event.event_type] || 'mdiBell'} size={16} />
 								</span>
 								<span class="text-sm font-medium truncate">{event.collection_name}</span>
-								<span class="event-badge">{event.event_type.replace('_', ' ')}</span>
+								<span class="event-badge">{t(eventLabels[event.event_type] || event.event_type)}</span>
 							</div>
 							<span class="text-xs whitespace-nowrap font-mono" style="color: var(--color-muted-foreground);">{timeAgo(event.created_at)}</span>
 						</div>