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/translate.py

@@ -1,5 +1,5 @@
 from fastapi import APIRouter, HTTPException, Response, Depends
-from typing import Optional, Dict, Any, Annotated
+from typing import Optional, Dict, Any
 from pydantic import BaseModel
 from sqlalchemy.ext.asyncio import AsyncSession
 from app.database import get_db
@@ -51,7 +51,7 @@ async def translate_text(
 async def generate_reply(
     data: ReplyRequest,
     user_id: str = Depends(get_current_user_id),
-    db: Annotated[AsyncSession, Depends(get_db)] = None,
+    db: AsyncSession = Depends(get_db),
 ):
     pref_service = UserPreferenceService(db)
     pref_context = await pref_service.get_preference_context(user_id, "reply")