fix(tabs): replace SingleTickerProviderStateMixin with TickerProviderStateMixin

_buildTabs creates a new TabController (new ticker) before disposing the
old one, so two tickers briefly coexist — SingleTickerProviderStateMixin
throws. TickerProviderStateMixin supports multiple concurrent tickers.

Co-Authored-By: claude-flow <ruv@ruv.net>

lib/screens/programmer_tasks/programmer_tasks_list_screen.dart

@@ -29,7 +29,7 @@ class ProgrammerTasksListScreen extends ConsumerStatefulWidget {
 
 class _ProgrammerTasksListScreenState
     extends ConsumerState<ProgrammerTasksListScreen>
-    with SingleTickerProviderStateMixin {
+    with TickerProviderStateMixin {
   late TabController _tabController;
   late List<ProgrammerTasksTab> _tabs;
   bool _tabsBuilt = false;