refactor: remove unreachable code paths and unused members

Drops dead code across services, models, utils and widgets, including the
connection auth service, which had no implementer, and the Live TV DVR
provisioning models, which had no caller.

Tests that only covered deleted behaviour are removed or trimmed. No
behaviour change.

lib/services/api_cache.dart

@@ -166,27 +166,6 @@ abstract class ApiCache {
     await (_db.delete(_db.apiCache)..where((t) => t.pinned.equals(false))).go();
   }
 
-  /// Pin every row whose `cacheKey` matches the SQL `LIKE` [pattern]. Used by
-  /// backend subclasses that pin by item-shape rather than a single endpoint
-  /// (e.g. Jellyfin's per-user item rows where the user segment is a
-  /// wildcard).
-  Future<void> pinByKeyPattern(String pattern) async {
-    await (_db.update(
-      _db.apiCache,
-    )..where((t) => t.cacheKey.like(pattern))).write(const ApiCacheCompanion(pinned: Value(true)));
-  }
-
-  Future<void> unpinByKeyPattern(String pattern) async {
-    await (_db.update(
-      _db.apiCache,
-    )..where((t) => t.cacheKey.like(pattern))).write(const ApiCacheCompanion(pinned: Value(false)));
-  }
-
-  Future<bool> hasPinnedMatching(String pattern) async {
-    final rows = await (_db.select(_db.apiCache)..where((t) => t.cacheKey.like(pattern) & t.pinned.equals(true))).get();
-    return rows.isNotEmpty;
-  }
-
   /// Pull pinned rows for [serverId] and extract the first capture group of
   /// [keyPattern] from each `cacheKey`. Returns the unique set of captured
   /// ids — backend subclasses use this to enumerate their pinned items