feat: create project folders from desktop app

SovereignAI-Starter/flutter_app/test/project_folder_service_test.dart

@@ -0,0 +1,65 @@
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:flutter_app/core/projects/project_folder_service.dart';
+
+void main() {
+  test('creates a new project folder under the chosen parent', () async {
+    final parent = await Directory.systemTemp.createTemp(
+      'mithqal-project-parent-',
+    );
+    addTearDown(() => parent.delete(recursive: true));
+
+    final createdPath = await createProjectFolder(parent.path, 'تجربة أولى');
+
+    expect(await Directory(createdPath).exists(), isTrue);
+    expect(
+      Directory(createdPath).parent.resolveSymbolicLinksSync(),
+      parent.path,
+    );
+  });
+
+  test('rejects unsafe, hidden, reserved, and empty project names', () async {
+    final parent = await Directory.systemTemp.createTemp(
+      'mithqal-project-invalid-',
+    );
+    addTearDown(() => parent.delete(recursive: true));
+
+    for (final name in [
+      '',
+      '.',
+      '..',
+      '.hidden',
+      r'a\b',
+      'CON',
+      'node_modules',
+    ]) {
+      await expectLater(
+        createProjectFolder(parent.path, name),
+        throwsArgumentError,
+      );
+    }
+    expect(await parent.list().isEmpty, isTrue);
+  });
+
+  test('does not overwrite an existing file or directory', () async {
+    final parent = await Directory.systemTemp.createTemp(
+      'mithqal-project-collision-',
+    );
+    addTearDown(() => parent.delete(recursive: true));
+    await Directory(
+      '${parent.path}${Platform.pathSeparator}already-there',
+    ).create();
+
+    await expectLater(
+      createProjectFolder(parent.path, 'already-there'),
+      throwsArgumentError,
+    );
+    expect(
+      await Directory(
+        '${parent.path}${Platform.pathSeparator}already-there',
+      ).exists(),
+      isTrue,
+    );
+  });
+}