refactor(database): remove unused table mapping and data classes

- Deleted table `map` methods, data classes, and companions in schema verification code.
- Updated migrations for more precise version checks.

lib/core/database/database.dart

@@ -69,7 +69,7 @@ class AppDatabase extends _$AppDatabase {
           await m.createTable(tasks);
           await m.createTable(taskCompletions);
         }
-        if (from < 3) {
+        if (from == 2) {
           await m.addColumn(tasks, tasks.isActive);
         }
       },