fix(lint): move sqlite3 to dependencies, use close() instead of dispose()

- sqlite3 is now imported in lib/ (production code), so it must be a
  regular dependency, not a dev_dependency
- Replace deprecated conn.dispose() with conn.close() in the test

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pubspec.yaml

@@ -19,6 +19,7 @@ dependencies:
 
   # Local persistence (offline-first)
   drift: ^2.20.3
+  sqlite3: ^3.1.5  # used directly in lib/data/db/database.dart (_setupPragmas)
   sqlite3_flutter_libs: ^0.6.0+eol
   path_provider: ^2.1.5
   path: ^1.9.1
@@ -78,7 +79,6 @@ dev_dependencies:
   mockito: ^5.4.4
   fake_async: ^1.3.1
   path_provider_platform_interface: ^2.1.2
-  sqlite3: ^3.1.5  # used directly in test/unit/db_test_helper.dart; 3.x required for Database.close()
   url_launcher_platform_interface: ^2.3.2
   plugin_platform_interface: ^2.1.8
   flutter_launcher_icons: ^0.14.0

test/unit/migration_test.dart

@@ -541,8 +541,8 @@ void main() {
         expect(() => setupPragmasForTesting(conn2), returnsNormally);
 
         conn1.execute('ROLLBACK;');
-        conn1.dispose();
-        conn2.dispose();
+        conn1.close();
+        conn2.close();
       },
     );
   });