feat(portals): find the same movie in your other playlists

A movie that exists in several imported Xtream playlists now shows a
"Sources N" chip on its detail page and in the player. Switching playlist
mid-film keeps the timecode, a preferred source can be pinned per movie, and
a failed stream offers the alternatives instead of a dead end.

The governing rule is that a guess is never presented as a fact. Every
metadata value carries where it came from — `api` (the provider said so),
`parsed` (inferred from the title) or `probe` (we contacted the stream).
Facts render as plain tags, guesses are prefixed `~` in a warning colour, and
an unknown value renders no tag at all plus a "check" affordance. Ranking and
failover read through `factualOnly()`, so a filename claiming 4K is
structurally unable to outrank a source that was actually reached. A probe
that could not complete reports "unknown", never "unavailable".

Scope is deliberately narrow: Xtream to Xtream, movies only, Electron only.
Stalker never reaches the `content` table and M3U is a JSON blob whose search
forces live content; both are additive later, since the candidate type
already carries all three portal kinds. In the PWA every entry point is gated
off and the chip renders nothing.

Auto-failover is opt-in and off by default. Each source is tried at most once
per session, so it terminates structurally, and the switch is never silent —
the toast names the new playlist, offers an undo, and warns that the dub may
differ only when both sides state an audio track as fact.

Notable details:
- Playlist names are routinely the pasted URL, credentials included. They are
  never rendered raw; a short host-only label is derived instead.
- Quality is derived from pixel width, not height: a 2.39:1 1080p master is
  1920x800, and bucketing that by height would publish "720p" as a fact.
- Switching is a single `inlinePlayback.set()` so the player and engine
  survive and re-seek; the carried position is read before the 15s
  persistence throttle so it does not rewind.
- Sources from one playlist collapse into a group, since the same film often
  appears there several times under different stream ids.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

apps/electron-backend/src/app/workers/database.worker.ts

@@ -4,6 +4,7 @@ import {
 } from './database.worker-connection';
 import { parentPort } from 'worker_threads';
 import type {
+    VodSourcePin,
     XtreamBackupFavoriteItem,
     XtreamBackupRecentlyViewedItem,
 } from '@iptvnator/shared/interfaces';
@@ -78,12 +79,21 @@ import {
     removeRecentItemsBatch,
 } from '../database/operations/recently-viewed.operations';
 import { matchTitles } from '../database/operations/title-match.operations';
+import {
+    findTitleSources,
+    type FindTitleSourcesRequest,
+} from '../database/operations/title-sources.operations';
 import {
     clearTmdbMetadata,
     getTmdbCacheStats,
     getTmdbMetadata,
     setTmdbMetadata,
 } from '../database/operations/tmdb.operations';
+import {
+    clearVodSourcePin,
+    getVodSourcePin,
+    setVodSourcePin,
+} from '../database/operations/vod-source-pin.operations';
 import {
     deleteXtreamContent,
     restoreXtreamUserData,
@@ -702,6 +712,28 @@ async function executeRequest(
             return matchTitles(db, payload.titles);
         }
 
+        case 'DB_FIND_TITLE_SOURCES': {
+            const payload = message.payload as {
+                request: FindTitleSourcesRequest;
+            };
+            return findTitleSources(db, payload.request);
+        }
+
+        case 'DB_GET_VOD_SOURCE_PIN': {
+            const payload = message.payload as { matchKeys: string[] };
+            return getVodSourcePin(db, payload.matchKeys);
+        }
+
+        case 'DB_SET_VOD_SOURCE_PIN': {
+            const payload = message.payload as { pin: VodSourcePin };
+            return setVodSourcePin(db, payload.pin);
+        }
+
+        case 'DB_CLEAR_VOD_SOURCE_PIN': {
+            const payload = message.payload as { matchKeys: string[] };
+            return clearVodSourcePin(db, payload.matchKeys);
+        }
+
         case 'DB_DELETE_ALL_PLAYLISTS': {
             const payload = message.payload as { operationId?: string };