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/l10n/app_localizations_zh.dart

@@ -1171,6 +1171,60 @@ class AppLocalizationsZh extends AppLocalizations {
 
   @override
   String get settingsDoNotSellDisabled => '已开启';
+
+  @override
+  String get settingsFeedbackTitle => '意见反馈';
+
+  @override
+  String get feedbackTitle => '意见反馈';
+
+  @override
+  String get feedbackTypeLabel => '反馈类型';
+
+  @override
+  String get feedbackTypeBug => '问题反馈';
+
+  @override
+  String get feedbackTypeSuggestion => '功能建议';
+
+  @override
+  String get feedbackTypeOther => '其他';
+
+  @override
+  String get feedbackContentLabel => '反馈内容';
+
+  @override
+  String get feedbackContentHint => '请详细描述您的问题或建议...';
+
+  @override
+  String get feedbackImagesLabel => '添加截图（最多3张）';
+
+  @override
+  String get feedbackAnonymousLabel => '不上传我的个人信息';
+
+  @override
+  String get feedbackAnonymousHint => '勾选后将不采集您的用户ID，仅采集设备信息用于问题排查';
+
+  @override
+  String get feedbackSubmit => '提交反馈';
+
+  @override
+  String get feedbackSubmitting => '提交中...';
+
+  @override
+  String get feedbackSuccess => '感谢您的反馈，我们会尽快处理';
+
+  @override
+  String get feedbackContentRequired => '请输入反馈内容';
+
+  @override
+  String get feedbackContentTooLong => '反馈内容不能超过500字';
+
+  @override
+  String get feedbackTooManyImages => '最多只能上传3张图片';
+
+  @override
+  String get feedbackImageTooLarge => '图片大小不能超过5MB';
 }
 
 /// The translations for Chinese, using the Han script (`zh_Hant`).
@@ -2096,4 +2150,58 @@ class AppLocalizationsZhHant extends AppLocalizationsZh {
 
   @override
   String get settingsDoNotSellDisabled => '已開啟';
+
+  @override
+  String get settingsFeedbackTitle => '意見回饋';
+
+  @override
+  String get feedbackTitle => '意見回饋';
+
+  @override
+  String get feedbackTypeLabel => '回饋類型';
+
+  @override
+  String get feedbackTypeBug => '問題回饋';
+
+  @override
+  String get feedbackTypeSuggestion => '功能建議';
+
+  @override
+  String get feedbackTypeOther => '其他';
+
+  @override
+  String get feedbackContentLabel => '回饋內容';
+
+  @override
+  String get feedbackContentHint => '請詳細描述您的問題或建議...';
+
+  @override
+  String get feedbackImagesLabel => '添加截圖（最多3張）';
+
+  @override
+  String get feedbackAnonymousLabel => '不上傳我的個人信息';
+
+  @override
+  String get feedbackAnonymousHint => '勾選後將不採集您的用戶ID，僅採集設備信息用於問題排查';
+
+  @override
+  String get feedbackSubmit => '提交回饋';
+
+  @override
+  String get feedbackSubmitting => '提交中...';
+
+  @override
+  String get feedbackSuccess => '感謝您的回饋，我們會盡快處理';
+
+  @override
+  String get feedbackContentRequired => '請輸入回饋內容';
+
+  @override
+  String get feedbackContentTooLong => '回饋內容不能超過500字';
+
+  @override
+  String get feedbackTooManyImages => '最多只能上傳3張圖片';
+
+  @override
+  String get feedbackImageTooLarge => '圖片大小不能超過5MB';
 }