Add Drift SQLite database for local task storage

- Create AppDatabase with Tasks table
- Add CRUD operations for local task persistence
- Include generated database code

lib/core/database/app_database.dart

@@ -0,0 +1,70 @@
+import 'dart:io';
+
+import 'package:drift/drift.dart';
+import 'package:drift/native.dart';
+import 'package:path_provider/path_provider.dart';
+import 'package:path/path.dart' as p;
+
+part 'app_database.g.dart';
+
+class Tasks extends Table {
+  TextColumn get id => text()();
+  TextColumn get title => text().withLength(min: 1, max: 500)();
+  TextColumn get description => text().nullable()();
+  DateTimeColumn get date => dateTime()();
+  TextColumn get time => text().nullable()();
+  TextColumn get priority => text().withDefault(const Constant('medium'))();
+  BoolColumn get isDone => boolean().withDefault(const Constant(false))();
+  DateTimeColumn get createdAt => dateTime().withDefault(currentDateAndTime)();
+  DateTimeColumn get updatedAt => dateTime().withDefault(currentDateAndTime)();
+
+  @override
+  Set<Column> get primaryKey => {id};
+}
+
+@DriftDatabase(tables: [Tasks])
+class AppDatabase extends _$AppDatabase {
+  AppDatabase() : super(_openConnection());
+
+  @override
+  int get schemaVersion => 1;
+
+  // Task CRUD operations
+  Future<List<Task>> getTasksByDate(DateTime date) {
+    final startOfDay = DateTime(date.year, date.month, date.day);
+    final endOfDay = startOfDay.add(const Duration(days: 1));
+    return (select(tasks)
+          ..where((t) => t.date.isBiggerOrEqualValue(startOfDay))
+          ..where((t) => t.date.isSmallerThanValue(endOfDay))
+          ..orderBy([(t) => OrderingTerm.asc(t.priority)]))
+        .get();
+  }
+
+  Future<Task?> getTaskById(String id) {
+    return (select(tasks)..where((t) => t.id.equals(id))).getSingleOrNull();
+  }
+
+  Future<int> insertTask(TasksCompanion task) {
+    return into(tasks).insert(task);
+  }
+
+  Future<bool> updateTask(TasksCompanion task) {
+    return update(tasks).replace(task);
+  }
+
+  Future<int> deleteTaskById(String id) {
+    return (delete(tasks)..where((t) => t.id.equals(id))).go();
+  }
+
+  Future<List<Task>> getAllTasks() {
+    return select(tasks).get();
+  }
+}
+
+LazyDatabase _openConnection() {
+  return LazyDatabase(() async {
+    final dbFolder = await getApplicationDocumentsDirectory();
+    final file = File(p.join(dbFolder.path, 'agenda_tasks.sqlite'));
+    return NativeDatabase.createInBackground(file);
+  });
+}