remove jellyfin, mqtt, webhook services, fix tests, add schema migrations

- delete server/services/jellyfin.ts, webhook.ts, mqtt.ts and their tests
- strip jellyfin/mqtt imports and startup calls from index.tsx and settings.ts
- remove /jellyfin, /mqtt, /mqtt/status, /mqtt/test, /jellyfin/webhook-plugin endpoints from settings router
- clean ENV_MAP and isEnvConfigured of jellyfin/mqtt keys
- add db/index.ts migrations for series_key, duration_seconds, scan_status, scan_error, last_scanned_at (new columns absent on older dev DBs)
- move idx_media_items_series_key out of SCHEMA into migrate() so it runs after the column is added
- fix all test fixtures: drop jellyfin_id/series_jellyfin_id column refs, update MediaItem/MediaStream object literals to match current types

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/api/__tests__/review.test.ts

@@ -10,8 +10,8 @@ function makeDb(): Database {
 		if (trimmed) db.run(trimmed);
 	}
 	db
-		.prepare("INSERT INTO media_items (id, jellyfin_id, type, name, file_path) VALUES (?, ?, 'Movie', 'T', '/x.mkv')")
-		.run(1, "jf-1");
+		.prepare("INSERT INTO media_items (id, type, name, file_path) VALUES (?, 'Movie', 'T', '/x.mkv')")
+		.run(1);
 	return db;
 }