fix(plex): tolerate account-API schema drift in profile and switch parsing

Around July 3 plex.tv started returning the profile language-list fields
(defaultAudioLanguages, defaultSubtitleLanguages, mediaReviewsLanguages)
as comma-separated strings instead of arrays. The generated cast threw on
the successful 201 /switch response, dropping the freshly minted Home
user token: every rebind failed, the binder retried a /switch mint every
1-2s, and the app sat permanently in offline mode even after re-signing
in. Accounts without language prefs set were unaffected, which is why
the breakage looked sporadic.

Parse the language lists with a CSV-aware coercion, and make
UserSwitchResponse.fromJson strict only about authToken: decorative
fields now coerce tolerantly and a broken profile blob falls back to
defaults, so account-API drift can never brick token minting again.

close #1488

test/profiles/plex_home_switch_test.dart

@@ -0,0 +1,155 @@
+import 'dart:convert';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:http/http.dart' as http;
+import 'package:http/testing.dart';
+import 'package:plezy/i18n/strings.g.dart';
+import 'package:plezy/profiles/plex_home_switch.dart';
+import 'package:plezy/services/plex_auth_service.dart';
+import 'package:plezy/utils/media_server_http_client.dart';
+
+/// Regression for #1488: Plex started returning profile language lists as CSV
+/// strings ("en,sv") instead of arrays; the parse crash on the 201 /switch
+/// response made the flow report failure and drop the freshly minted token,
+/// leaving the app permanently offline.
+void main() {
+  setUpAll(() {
+    LocaleSettings.setLocaleSync(AppLocale.en);
+  });
+
+  PlexAuthService authReturning(MockClient mock) {
+    final client = MediaServerHttpClient(client: mock);
+    addTearDown(client.close);
+    return PlexAuthService.forTesting(http: client);
+  }
+
+  group('switchPlexHomeUserWithPin', () {
+    test('succeeds and keeps the token when the 201 body has drifted field shapes', () async {
+      final auth = authReturning(
+        MockClient((request) async {
+          expect(request.method, 'POST');
+          expect(request.url.path, '/api/v2/home/users/uuid-1/switch');
+          return http.Response(jsonEncode(_driftedSwitchBody()), 201, headers: {'content-type': 'application/json'});
+        }),
+      );
+
+      final result = await switchPlexHomeUserWithPin(
+        auth: auth,
+        accountToken: 'account-token',
+        homeUserUuid: 'uuid-1',
+        requiresPin: false,
+        promptForPin: ({String? errorMessage}) async => fail('should not prompt'),
+      );
+
+      expect(result.status, PlexHomeSwitchStatus.success);
+      expect(result.userToken, 'minted-user-token');
+    });
+
+    test('re-prompts on Plex error 1041 and succeeds with the corrected PIN', () async {
+      var attempts = 0;
+      final auth = authReturning(
+        MockClient((request) async {
+          attempts++;
+          if (attempts == 1) {
+            return http.Response(
+              jsonEncode({
+                'errors': [
+                  {'code': 1041, 'message': 'Invalid PIN', 'status': 403},
+                ],
+              }),
+              403,
+              headers: {'content-type': 'application/json'},
+            );
+          }
+          expect(request.url.queryParameters['pin'], '1234');
+          return http.Response(jsonEncode(_driftedSwitchBody()), 201, headers: {'content-type': 'application/json'});
+        }),
+      );
+
+      final promptErrors = <String?>[];
+      final result = await switchPlexHomeUserWithPin(
+        auth: auth,
+        accountToken: 'account-token',
+        homeUserUuid: 'uuid-1',
+        requiresPin: false,
+        promptForPin: ({String? errorMessage}) async {
+          promptErrors.add(errorMessage);
+          return '1234';
+        },
+      );
+
+      expect(result.status, PlexHomeSwitchStatus.success);
+      expect(result.userToken, 'minted-user-token');
+      expect(attempts, 2);
+      expect(promptErrors, hasLength(1));
+      expect(promptErrors.single, isNotNull);
+    });
+
+    test('reports cancelled when the user dismisses the PIN prompt', () async {
+      final auth = authReturning(
+        MockClient((request) async {
+          return http.Response(
+            jsonEncode({
+              'errors': [
+                {'code': 1041, 'message': 'Invalid PIN', 'status': 403},
+              ],
+            }),
+            403,
+            headers: {'content-type': 'application/json'},
+          );
+        }),
+      );
+
+      final result = await switchPlexHomeUserWithPin(
+        auth: auth,
+        accountToken: 'account-token',
+        homeUserUuid: 'uuid-1',
+        requiresPin: false,
+        promptForPin: ({String? errorMessage}) async => null,
+      );
+
+      expect(result.status, PlexHomeSwitchStatus.cancelled);
+      expect(result.userToken, isNull);
+    });
+
+    test('reports failed when the response has no token', () async {
+      final auth = authReturning(
+        MockClient((request) async {
+          return http.Response(
+            jsonEncode({'id': 1, 'uuid': 'uuid-1'}),
+            201,
+            headers: {'content-type': 'application/json'},
+          );
+        }),
+      );
+
+      final result = await switchPlexHomeUserWithPin(
+        auth: auth,
+        accountToken: 'account-token',
+        homeUserUuid: 'uuid-1',
+        requiresPin: false,
+        promptForPin: ({String? errorMessage}) async => fail('should not prompt'),
+      );
+
+      expect(result.status, PlexHomeSwitchStatus.failed);
+      expect(result.userToken, isNull);
+    });
+  });
+}
+
+Map<String, dynamic> _driftedSwitchBody() => {
+  'id': 312174832,
+  'uuid': 'uuid-1',
+  'title': 'hi_phi',
+  'authToken': 'minted-user-token',
+  'protected': true,
+  'home': true,
+  'profile': {
+    'defaultAudioLanguage': 'en',
+    'defaultAudioLanguages': 'en,sv',
+    'defaultSubtitleLanguage': 'en',
+    'defaultSubtitleLanguages': 'en,sv',
+    'mediaReviewsLanguages': null,
+    'mediaPostsVisibility': true,
+  },
+};