fix: Use ON DELETE CASCADE for the anime watcher join table

lib/src/ui/pages/main_page.dart

@@ -1,14 +0,0 @@
-import 'package:anitrack/src/ui/helpers.dart';
-import 'package:flutter/material.dart';
-
-/// A page that renders the anime list and the calendar as nested views.
-class MainPage extends StatelessWidget {
-  const MainPage({super.key});
-
-  @override
-  Widget build(BuildContext context) {
-    return Scaffold(
-      drawer: getDrawer(context),
-    );
-  }
-}