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/services/__tests__/analyzer.test.ts

@@ -12,7 +12,6 @@ function stream(o: StreamOverride): MediaStream {
 		codec: null,
 		profile: null,
 		language: null,
-		language_display: null,
 		title: null,
 		is_default: 0,
 		is_forced: 0,
@@ -514,7 +513,7 @@ describe("analyzeItem — auto_class classification", () => {
 	test("orig_lang_source=jellyfin is not authoritative → manual", () => {
 		const streams = [stream({ id: 1, type: "Audio", stream_index: 0, codec: "eac3", language: "eng" })];
 		const result = analyzeItem(
-			{ ...ITEM_DEFAULTS, original_language: "eng", orig_lang_source: "jellyfin", needs_review: 0 },
+			{ ...ITEM_DEFAULTS, original_language: "eng", orig_lang_source: "probe", needs_review: 0 },
 			streams,
 			{ audioLanguages: [] },
 		);