hardened API decoding against server fields the models did not expect

The Talk room list crashed for a new account because the server omits
lastMessage for rooms without a visible message and the model required it.
Beyond that single field, a review of the Talk models against the OpenAPI
spec of the installed version (23.0.8) found the same crash class in several
places: closed enums over open server values (inCall bitmask, rich-object
types, actor and message types), a deleted parent sent as {id, deleted},
and the autocomplete status arriving as an object.

- json_serializable `checked: true`: decode errors now name class and field
- lists (rooms, messages, participants, autocomplete) decode per entry;
  a malformed entry is skipped and reported via ClientErrorReporter
- unknownEnumValue fallbacks for all response enums of Talk and breakers
- lastMessage nullable; inCall as bitmask; deleted parent placeholder;
  autocomplete status object/string; fixed shareWithDisplayNameUnique key
- GetRoomParams no longer sends null query parameters

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HrepDTL4qDe35TuS29sLW3

lib/api/marianumconnect/queries/timetable_get_holidays/timetable_get_holidays_response.g.dart

@@ -8,15 +8,23 @@ part of 'timetable_get_holidays_response.dart';
 
 TimetableGetHolidaysResponse _$TimetableGetHolidaysResponseFromJson(
   Map<String, dynamic> json,
-) =>
-    TimetableGetHolidaysResponse(
-        result: (json['result'] as List<dynamic>)
-            .map((e) => McHoliday.fromJson(e as Map<String, dynamic>))
-            .toList(),
-      )
-      ..headers = (json['headers'] as Map<String, dynamic>?)?.map(
-        (k, e) => MapEntry(k, e as String),
-      );
+) => $checkedCreate('TimetableGetHolidaysResponse', json, ($checkedConvert) {
+  final val = TimetableGetHolidaysResponse(
+    result: $checkedConvert(
+      'result',
+      (v) => (v as List<dynamic>)
+          .map((e) => McHoliday.fromJson(e as Map<String, dynamic>))
+          .toList(),
+    ),
+  );
+  $checkedConvert(
+    'headers',
+    (v) => val.headers = (v as Map<String, dynamic>?)?.map(
+      (k, e) => MapEntry(k, e as String),
+    ),
+  );
+  return val;
+});
 
 Map<String, dynamic> _$TimetableGetHolidaysResponseToJson(
   TimetableGetHolidaysResponse instance,