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/whatsapp.py

@@ -1,7 +1,7 @@
 from fastapi import APIRouter, Request, HTTPException, Depends, Header
 from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy import select, and_
-from typing import Annotated, Optional
+from typing import Optional
 from pydantic import BaseModel
 from app.database import get_db
 from app.services.whatsapp import WhatsAppService
@@ -30,7 +30,7 @@ async def verify_webhook(
 async def handle_webhook(
     request: Request,
     x_hub_signature_256: Optional[str] = Header(None),
-    db: Annotated[AsyncSession, Depends(get_db)] = None,
+    db: AsyncSession = Depends(get_db),
 ):
     svc = WhatsAppService()
     body = await request.body()
@@ -80,7 +80,7 @@ class SendMessageRequest(BaseModel):
 async def send_message(
     data: SendMessageRequest,
     user_id: str = Depends(get_current_user_id),
-    db: Annotated[AsyncSession, Depends(get_db)] = None,
+    db: AsyncSession = Depends(get_db),
 ):
     svc = WhatsAppService()