feat: UX & notification improvements — icons, events, chat names, link validation, templates

- Show entity icons on all cards with fallback defaults (providers, trackers, targets, bots)
- Enrich EventLog with provider_name, tracker_name, assets_count; add DB migration
- Dashboard events: filtering (type, provider, search), sorting, pagination, dynamic page size
- Friendly chat names on telegram target cards (resolve from TelegramChat table)
- Test message button on bot chat items with locale-aware messages
- Album public link validation on tracker save with auto-create dialog
- Support albums without public links: conditional <a href> in templates
- Fetch shared links during poll, enrich events with public_url/protected_url
- Per-asset public_url in template context ({share_url}/photos/{asset_id})
- Common date/location detection: common_date + common_location context vars
- Dual date formats: date_format (datetime) + date_only_format (date only)
- Template clone button, HTML link rendering in template preview
- Fix Telegram asset download 401: pass x-api-key headers through client
- Fix provider external_url matching for API key scoping
- Fix event timestamp timezone (append Z suffix for UTC)
- Localize event filter controls, test messages (EN/RU)
- Template variable UI helpers updated with all new fields
- CLAUDE.md: template system sync rules documentation

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

frontend/src/routes/providers/+page.svelte

@@ -155,9 +155,7 @@
 				<div class="flex items-center justify-between">
 					<div class="flex items-center gap-3">
 						<div class="health-dot {health[provider.id] === true ? 'online' : health[provider.id] === false ? 'offline' : 'checking'}"></div>
-						{#if provider.icon}
-							<span style="color: var(--color-primary);"><MdiIcon name={provider.icon} size={20} /></span>
-						{/if}
+						<span style="color: var(--color-primary);"><MdiIcon name={provider.icon || 'mdiServer'} size={20} /></span>
 						<div>
 							<div class="flex items-center gap-2">
 								<p class="font-medium">{provider.name}</p>