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/notification.py

@@ -1,6 +1,6 @@
 from fastapi import APIRouter, Depends, HTTPException, Query
 from sqlalchemy.ext.asyncio import AsyncSession
-from typing import Annotated, Optional
+from typing import Optional
 from app.database import get_db
 from app.services.notification import NotificationService
 from app.api.v1.deps import get_current_user_id
@@ -14,7 +14,7 @@ async def list_notifications(
     size: int = Query(20, ge=1, le=100),
     unread_only: bool = Query(False),
     user_id: str = Depends(get_current_user_id),
-    db: Annotated[AsyncSession, Depends(get_db)] = None,
+    db: AsyncSession = Depends(get_db),
 ):
     service = NotificationService(db)
     return await service.list_notifications(user_id, page, size, unread_only)
@@ -23,7 +23,7 @@ async def list_notifications(
 @router.get("/unread-count")
 async def unread_count(
     user_id: str = Depends(get_current_user_id),
-    db: Annotated[AsyncSession, Depends(get_db)] = None,
+    db: AsyncSession = Depends(get_db),
 ):
     service = NotificationService(db)
     count = await service.get_unread_count(user_id)
@@ -34,7 +34,7 @@ async def unread_count(
 async def mark_read(
     notification_id: str,
     user_id: str = Depends(get_current_user_id),
-    db: Annotated[AsyncSession, Depends(get_db)] = None,
+    db: AsyncSession = Depends(get_db),
 ):
     service = NotificationService(db)
     success = await service.mark_read(user_id, notification_id)
@@ -46,7 +46,7 @@ async def mark_read(
 @router.post("/read-all")
 async def mark_all_read(
     user_id: str = Depends(get_current_user_id),
-    db: Annotated[AsyncSession, Depends(get_db)] = None,
+    db: AsyncSession = Depends(get_db),
 ):
     service = NotificationService(db)
     count = await service.mark_all_read(user_id)
@@ -57,7 +57,7 @@ async def mark_all_read(
 async def delete_notification(
     notification_id: str,
     user_id: str = Depends(get_current_user_id),
-    db: Annotated[AsyncSession, Depends(get_db)] = None,
+    db: AsyncSession = Depends(get_db),
 ):
     service = NotificationService(db)
     success = await service.delete_notification(user_id, notification_id)