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/core/config/settings.py

@@ -153,8 +153,13 @@ class StorageSettings(BaseModel):
         bucket: str = Field(default="avatars", min_length=3, max_length=63)
         max_size_mb: int = Field(default=2, ge=1, le=10)
 
+    class FeedbackSettings(BaseModel):
+        bucket: str = Field(default="feedback-images", min_length=3, max_length=63)
+        max_size_mb: int = Field(default=5, ge=1, le=20)
+
     attachment: AttachmentSettings = Field(default_factory=AttachmentSettings)
     avatar: AvatarSettings = Field(default_factory=AvatarSettings)
+    feedback: FeedbackSettings = Field(default_factory=FeedbackSettings)
 
 
 class LlmSettings(BaseModel):
@@ -235,6 +240,22 @@ def _resolve_env_file() -> str:
 PROJECT_ROOT = _resolve_project_root()
 
 
+class FeedbackReportSettings(BaseModel):
+    email: str = Field(default="support@example.com", description="客服邮箱")
+    cron: str = Field(default="0 10 * * *", description="报告生成cron表达式")
+    enabled: bool = Field(default=False, description="是否启用报告推送")
+
+
+class EmailSettings(BaseModel):
+    host: str = Field(default="smtp.feishu.cn", description="SMTP 服务器地址")
+    port: int = Field(default=465, ge=1, le=65535, description="SMTP 端口")
+    username: str = Field(default="", description="SMTP 用户名")
+    password: SecretStr = Field(default=SecretStr(""), description="SMTP 密码")
+    use_ssl: bool = Field(default=True, description="是否使用 SSL")
+    from_address: str = Field(default="noreply@example.com", description="发件人地址")
+    from_name: str = Field(default="Eryao Feedback", description="发件人显示名称")
+
+
 class Settings(BaseSettings):
     runtime: RuntimeSettings = RuntimeSettings()
     cors: CorsSettings = CorsSettings()
@@ -250,6 +271,10 @@ class Settings(BaseSettings):
     taskiq: TaskiqSettings = Field(default_factory=TaskiqSettings)
     agent_runtime: AgentRuntimeSettings = Field(default_factory=AgentRuntimeSettings)
     points_policy: PointsPolicySettings = Field(default_factory=PointsPolicySettings)
+    feedback_report: FeedbackReportSettings = Field(
+        default_factory=FeedbackReportSettings
+    )
+    email: EmailSettings = Field(default_factory=EmailSettings)
 
     @computed_field
     @property