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

backend/src/services/base/supabase.py

@@ -110,6 +110,7 @@ class SupabaseService(BaseServiceProvider):
         buckets = [
             (config.storage.attachment.bucket, False),
             (config.storage.avatar.bucket, True),
+            (config.storage.feedback.bucket, False),
         ]
 
         def _check_and_create() -> None:
@@ -170,6 +171,7 @@ class SupabaseService(BaseServiceProvider):
         allowed_buckets = {
             config.storage.attachment.bucket,
             config.storage.avatar.bucket,
+            config.storage.feedback.bucket,
         }
         if bucket not in allowed_buckets:
             raise RuntimeError("Invalid storage bucket")