feat: Gemini AI (doc OCR + face match) + role-assignment endpoints

- GeminiService (integrations/gemini, @Global): extractDocument (OCR fields) + faceMatch; graceful if no GEMINI_API_KEY
- documents: face-match now real via Gemini; POST /admin/documents/:id/ocr extracts fields for CS auto-fill
- roles: PATCH /admin/users/:id/role (admin) + POST /platform/users/role (bootstrap via x-platform-secret)
- config: gemini + platform.secret; .env.example entries

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/driver/trip_overlay_plugin/example/integration_test/plugin_integration_test.dart

@@ -0,0 +1,25 @@
+// This is a basic Flutter integration test.
+//
+// Since integration tests run in a full Flutter application, they can interact
+// with the host side of a plugin implementation, unlike Dart unit tests.
+//
+// For more information about Flutter integration tests, please see
+// https://flutter.dev/to/integration-testing
+
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:integration_test/integration_test.dart';
+
+import 'package:trip_overlay_plugin/trip_overlay_plugin.dart';
+
+void main() {
+  IntegrationTestWidgetsFlutterBinding.ensureInitialized();
+
+  testWidgets('getPlatformVersion test', (WidgetTester tester) async {
+    final TripOverlayPlugin plugin = TripOverlayPlugin();
+    final String? version = await plugin.getPlatformVersion();
+    // The version string depends on the host platform running the test, so
+    // just assert that some non-empty string is returned.
+    expect(version?.isNotEmpty, true);
+  });
+}