fix(plex): surface server failures

lib/services/plex_client.dart

@@ -811,7 +811,7 @@ class PlexClient
   @override
   Future<HealthStatus> checkHealth() async {
     try {
-      final response = await _getWithFailover('/');
+      final response = await _getWithFailover('/', timeout: MediaServerTimeouts.plexProbe);
       return response.statusCode == 200 ? HealthStatus.online : HealthStatus.offline;
     } on MediaServerHttpException catch (e) {
       if (e.statusCode == 401 || e.statusCode == 403) return HealthStatus.authError;
@@ -841,7 +841,8 @@ class PlexClient
 
   /// Cancel a running background task by its UUID.
   Future<void> cancelActivity(String uuid) async {
-    await _http.delete('/activities/$uuid');
+    final response = await _http.delete('/activities/$uuid');
+    throwIfHttpError(response);
   }
 
   /// Get library sections
@@ -1699,7 +1700,8 @@ class PlexClient
   /// Remove item from Continue Watching (On Deck) without affecting watch status or progress
   /// This uses the same endpoint Plex Web uses to hide items from Continue Watching
   Future<void> removeFromOnDeck(String ratingKey) async {
-    await _http.put('/actions/removeFromContinueWatching', queryParameters: {'ratingKey': ratingKey});
+    final response = await _http.put('/actions/removeFromContinueWatching', queryParameters: {'ratingKey': ratingKey});
+    throwIfHttpError(response);
   }
 
   /// Delete a media item from the library
@@ -2585,6 +2587,7 @@ class PlexClient
         '/library/collections',
         queryParameters: {'type': ?type, 'title': title, 'smart': 0, 'sectionId': sectionId, 'uri': uri},
       );
+      throwIfHttpError(response);
       appLogger.d('Create collection response: ${response.statusCode}');
 
       // Extract the collection ID from the response
@@ -2713,6 +2716,7 @@ class PlexClient
       }
 
       final response = await _http.post('/playQueues', queryParameters: queryParams);
+      throwIfHttpError(response);
 
       return _parsePlayQueueResponse(
         response.data,
@@ -2951,7 +2955,8 @@ class PlexClient
 
   /// Empty trash for a library section
   Future<void> emptyLibraryTrash(String sectionId) async {
-    await _http.put('/library/sections/$sectionId/emptyTrash');
+    final response = await _http.put('/library/sections/$sectionId/emptyTrash');
+    throwIfHttpError(response);
   }
 
   /// Analyze library section

lib/services/plex_client/parts/live_tv.dart

@@ -1141,10 +1141,12 @@ mixin _PlexLiveTvClientMethods on MediaServerCacheMixin {
   /// Update favorite channels on the Plex cloud.
   Future<void> setFavoriteChannels(List<FavoriteChannel> channels) async {
     try {
-      await _http.put(
-        _favoriteChannelsUrl,
-        body: channels.map((c) => c.toJson()).toList(),
-        headers: _providerVersionHeader,
+      await _expectOk(
+        () => _http.put(
+          _favoriteChannelsUrl,
+          body: channels.map((c) => c.toJson()).toList(),
+          headers: _providerVersionHeader,
+        ),
       );
     } catch (e) {
       appLogger.e('Failed to update favorite channels', error: e);

lib/utils/media_server_timeouts.dart

@@ -44,6 +44,10 @@ class MediaServerTimeouts {
 
   static const plexTvReceive = Duration(seconds: 10);
 
+  /// Authenticated health probe timeout. Health sweeps await every server, so
+  /// a stale Plex endpoint must not hold the whole sweep for [receive].
+  static const plexProbe = Duration(seconds: 8);
+
   /// Probe + token-validate timeout — Jellyfin servers respond fast on
   /// `/System/Info/Public` and `/Users/Me`.
   static const jellyfinProbe = Duration(seconds: 8);

test/services/plex_client_http_contract_test.dart

@@ -0,0 +1,56 @@
+import 'package:drift/native.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:http/http.dart' as http;
+import 'package:http/testing.dart';
+import 'package:plezy/database/app_database.dart';
+import 'package:plezy/exceptions/media_server_exceptions.dart';
+import 'package:plezy/media/ids.dart';
+import 'package:plezy/models/plex/plex_config.dart';
+import 'package:plezy/services/plex_api_cache.dart';
+import 'package:plezy/services/plex_client.dart';
+
+void main() {
+  late AppDatabase db;
+
+  setUp(() {
+    db = AppDatabase.forTesting(NativeDatabase.memory());
+    PlexApiCache.initialize(db);
+  });
+
+  tearDown(() => db.close());
+
+  PlexClient makeClient(Future<http.Response> Function(http.Request request) handler) {
+    return PlexClient.forTesting(
+      config: PlexConfig(
+        baseUrl: 'https://plex.example.com',
+        token: 'token',
+        clientIdentifier: 'client-id',
+        product: 'Plezy',
+        version: '1',
+      ),
+      serverId: ServerId('server-id'),
+      httpClient: MockClient(handler),
+    );
+  }
+
+  test('void mutations surface non-success responses', () async {
+    final client = makeClient((_) async => http.Response('rejected', 500));
+    addTearDown(client.close);
+
+    for (final mutation in <Future<void> Function()>[
+      () => client.cancelActivity('activity-id'),
+      () => client.removeFromOnDeck('item-id'),
+      () => client.emptyLibraryTrash('library-id'),
+    ]) {
+      await expectLater(mutation(), throwsA(isA<MediaServerHttpException>()));
+    }
+  });
+
+  test('nullable creation APIs reject non-success response bodies', () async {
+    final client = makeClient((_) async => http.Response('rejected', 500));
+    addTearDown(client.close);
+
+    expect(await client.createCollectionFromUri(sectionId: '1', title: 'Collection', uri: 'server://items'), isNull);
+    expect(await client.createPlayQueue(uri: 'server://items', type: 'video'), isNull);
+  });
+}