feat: silent wechat login, marketing tab optimization, admin page foundation

- Add silent WeChat login for MP/browser environments
- Fix Python 3.6 compatibility (remove typing.Annotated usage)
- Marketing page: tab-based content generation with category support
- Translate page: add auto-detect language default
- Homepage: add TTS playback, announcement ticker, remove redundant quick-actions
- Fix FAB button overlap with custom tabbar on customers/quotation pages
- Make openai/anthropic imports lazy for Python 3.6 compat

backend/app/api/v1/feedback.py

@@ -1,6 +1,5 @@
 from fastapi import APIRouter, Depends, HTTPException
 from sqlalchemy.ext.asyncio import AsyncSession
-from typing import Annotated
 from pydantic import BaseModel
 from app.database import get_db
 from app.models.feedback import Feedback
@@ -19,7 +18,7 @@ class FeedbackRequest(BaseModel):
 async def submit_feedback(
     data: FeedbackRequest,
     user_id: str = Depends(get_current_user_id),
-    db: Annotated[AsyncSession, Depends(get_db)] = None,
+    db: AsyncSession = Depends(get_db),
 ):
     if not data.content.strip():
         raise HTTPException(status_code=400, detail="Content is required")