feat: NUT (Network UPS Tools) service provider + provider-agnostic UI

Add full NUT support as a polling-based service provider:
- Async TCP client for upsd protocol (port 3493, configurable)
- 8 event types: online, on_battery, low_battery, battery_restored,
  comms_lost, comms_restored, replace_battery, overload
- 3 bot commands: /status, /devices, /battery
- 38 Jinja2 templates (EN+RU notification + command templates)
- Database: tracking config fields, migration, seeds
- Frontend: provider form with host/port/credentials, grid items, i18n

Provider-agnostic UI improvements:
- Remove hardcoded 'immich' defaults from all config forms
- Dynamic collection labels per provider type (Albums/Repos/Boards/UPS Devices)
- Capability-driven test types instead of provider type checks
- Template variable helpers for all providers (was Immich-only)
- Guard Immich-only shared link check to Immich providers
- Auto-clear stale global provider filter from localStorage
- EntitySelect search placeholder shows current selection
- Fix noneLabel in linked target config selectors

New CLAUDE.md rule #8: no provider-specific hardcoding

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

@@ -35,7 +35,7 @@
 	let confirmDelete = $state<{ id: number; onconfirm: () => Promise<void> } | null>(null);
 
 	const defaultForm = () => ({
-		provider_type: 'immich', name: '', icon: '',
+		provider_type: '', name: '', icon: '',
 		// Immich event tracking
 		track_assets_added: true, track_assets_removed: false,
 		track_collection_renamed: true, track_collection_deleted: true, track_sharing_changed: false,