Restructure step 4: local library and media identity

- L1 (core, offline): release names with kinds (episode, movie, extra:
  OP/ED/Opening/Ending/NC/PV/OVA…), folder hints (season and name from
  parentheticals, ranges), one show across folders, gaps and next with
  skipped numbers, junk ignored, stable keys.
- L2 (app, device-owned cache): AniList match with synonyms and
  sequel walking, episode mapping across cours (AnimeFlow runs when
  signed in), art and episode titles, "Wrong show?" pins per show or
  folder, episode offsets; lazy, spaced requests, works offline.
- Files tab as a library: poster cards, show pages with banner, gap
  prompt, extras, movies, Wrong show? and Episode numbers.
- media.ref produced for local files, Jellyfin (provider ids) and links,
  carried in swaps and Up next; receivers name media from it.
- Hosting relays each Jellyfin item through its own server's login.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/desktop/lib/src/session/your_server.dart

@@ -8,7 +8,7 @@ import 'package:signals/signals.dart';
 import 'package:sync_relay_core/core.dart';
 
 import '../jellyfin/accounts.dart';
-import '../jellyfin/session_media.dart' show relayCredentialFor;
+import '../jellyfin/session_media.dart' show relayCredentialsFor;
 import '../state/connect_prefs.dart';
 import '../state/server_isolate.dart';
 import 'invite.dart';
@@ -60,7 +60,7 @@ class YourServer {
         _interfaces = interfaces ?? machineInterfaces;
 
   final ConnectStore forms;
-  /// Linked Jellyfin servers (default: the app's): the relay login.
+  /// Linked Jellyfin servers (default: the app's): the relay logins.
   final JellyfinAccounts? jellyfin;
   final Future<String> Function() _ytDlpDir;
   final String? Function() _logDir;
@@ -156,8 +156,8 @@ class YourServer {
         port: want,
         secret: form.hostSecret,
         // Guests without an account watch Jellyfin items through the
-        // server, with this app's own sign-in.
-        jellyfin: relayCredentialFor(_accounts),
+        // server, with this app's own sign-in on the item's server.
+        jellyfin: relayCredentialsFor(_accounts),
       );
       final invite = await inviteFor(bound, password: form.hostSecret.isNotEmpty);
       shared.value = invite;