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_zh.arb

@@ -487,5 +487,23 @@
   "settingsDoNotSellTitle": "个性化广告推荐",
   "settingsDoNotSellDescription": "关闭后，我们不会将您的个人信息用于广告推荐",
   "settingsDoNotSellEnabled": "已关闭",
-  "settingsDoNotSellDisabled": "已开启"
+  "settingsDoNotSellDisabled": "已开启",
+  "settingsFeedbackTitle": "意见反馈",
+  "feedbackTitle": "意见反馈",
+  "feedbackTypeLabel": "反馈类型",
+  "feedbackTypeBug": "问题反馈",
+  "feedbackTypeSuggestion": "功能建议",
+  "feedbackTypeOther": "其他",
+  "feedbackContentLabel": "反馈内容",
+  "feedbackContentHint": "请详细描述您的问题或建议...",
+  "feedbackImagesLabel": "添加截图（最多3张）",
+  "feedbackAnonymousLabel": "不上传我的个人信息",
+  "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",
+  "feedbackSubmit": "提交反馈",
+  "feedbackSubmitting": "提交中...",
+  "feedbackSuccess": "感谢您的反馈，我们会尽快处理",
+  "feedbackContentRequired": "请输入反馈内容",
+  "feedbackContentTooLong": "反馈内容不能超过500字",
+  "feedbackTooManyImages": "最多只能上传3张图片",
+  "feedbackImageTooLarge": "图片大小不能超过5MB"
 }