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

packages/server/src/notify_bridge_server/database/migrations.py

@@ -185,6 +185,41 @@ async def migrate_schema(engine: AsyncEngine) -> None:
                     )
                     logger.info("Added %s column to tracking_config table", col_name)
 
+        # Add NUT (UPS) tracking flags to tracking_config if missing
+        if await _has_table(conn, "tracking_config"):
+            nut_flags = [
+                ("track_ups_online", "INTEGER DEFAULT 1"),
+                ("track_ups_on_battery", "INTEGER DEFAULT 1"),
+                ("track_ups_low_battery", "INTEGER DEFAULT 1"),
+                ("track_ups_battery_restored", "INTEGER DEFAULT 1"),
+                ("track_ups_comms_lost", "INTEGER DEFAULT 1"),
+                ("track_ups_comms_restored", "INTEGER DEFAULT 1"),
+                ("track_ups_replace_battery", "INTEGER DEFAULT 1"),
+                ("track_ups_overload", "INTEGER DEFAULT 1"),
+            ]
+            for col_name, col_type in nut_flags:
+                if not await _has_column(conn, "tracking_config", col_name):
+                    await conn.execute(
+                        text(f"ALTER TABLE tracking_config ADD COLUMN {col_name} {col_type}")
+                    )
+                    logger.info("Added %s column to tracking_config table", col_name)
+
+        # Drop legacy template content columns from template_config
+        # (template content moved to template_slot child rows)
+        if await _has_table(conn, "template_config"):
+            legacy_cols = [
+                "message_assets_added", "message_assets_removed",
+                "message_collection_renamed", "message_collection_deleted",
+                "message_sharing_changed", "periodic_summary_message",
+                "scheduled_assets_message", "memory_mode_message",
+            ]
+            for col_name in legacy_cols:
+                if await _has_column(conn, "template_config", col_name):
+                    await conn.execute(
+                        text(f"ALTER TABLE template_config DROP COLUMN {col_name}")
+                    )
+                    logger.info("Dropped legacy column %s from template_config", col_name)
+
         # Add collection_name and shared to tracker_state if missing
         state_table = "notification_tracker_state" if await _has_table(conn, "notification_tracker_state") else "tracker_state"
         if await _has_table(conn, state_table):