feat(feedback): implement user feedback collection system with email reporting

Backend:
- Add user_feedback table with RLS policy
- Create feedback submission API (multipart/form-data)
- Implement xlsx report generation with embedded images
- Add scheduled email delivery via Feishu SMTP
- Create HTML email templates (daily_report, no_feedback)

Frontend:
- Add feedback screen with type selection and image picker
- Support anonymous submission via skipAuth flag
- Collect device info and app version

Protocol:
- Document feedback API contract and error codes
- Update http-error-codes.md with FEEDBACK_* codes

apps/lib/features/settings/data/repositories/feedback_repository.dart

@@ -0,0 +1,44 @@
+import 'package:image_picker/image_picker.dart';
+
+import '../apis/feedback_api.dart';
+import '../models/feedback.dart';
+
+abstract class FeedbackRepository {
+  Future<void> submitFeedback({
+    required FeedbackType type,
+    required String content,
+    required DeviceInfo deviceInfo,
+    required String appVersion,
+    required String osVersion,
+    required List<XFile> images,
+    required bool isAnonymous,
+  });
+}
+
+class FeedbackRepositoryImpl implements FeedbackRepository {
+  FeedbackRepositoryImpl({required FeedbackApi feedbackApi})
+    : _feedbackApi = feedbackApi;
+
+  final FeedbackApi _feedbackApi;
+
+  @override
+  Future<void> submitFeedback({
+    required FeedbackType type,
+    required String content,
+    required DeviceInfo deviceInfo,
+    required String appVersion,
+    required String osVersion,
+    required List<XFile> images,
+    required bool isAnonymous,
+  }) {
+    return _feedbackApi.submitFeedback(
+      type: type,
+      content: content,
+      deviceInfo: deviceInfo,
+      appVersion: appVersion,
+      osVersion: osVersion,
+      images: images,
+      isAnonymous: isAnonymous,
+    );
+  }
+}