feat: WeChat Pay integration, translation quota management, login UX fixes

- WeChat Pay APIv3 integration (JSAPI + Native) with cert-based auth
- TranslationQuota model + admin management UI (配额 tab)
- Alibaba MT provider now checks quota before translation
- Fix: admin tabs scrollable on mobile, remove header-card
- Fix: profile/login navigation - logout stays on profile, login returns to profile
- Fix: login form now visible by default (no extra click to show)
- Fix: home page translate link uses navigateTo (was switchTab to non-tabBar page)
- Add .coverage and apiclient_key.pem to gitignore

backend/app/api/v1/payment.py

@@ -1,8 +1,10 @@
-from fastapi import APIRouter, Depends, HTTPException
+from fastapi import APIRouter, Depends, HTTPException, Request
 from sqlalchemy.ext.asyncio import AsyncSession
 from pydantic import BaseModel
+from typing import Optional
 from app.database import get_db
 from app.services.payment import PaymentService
+from app.services.wechat_pay import WeChatPayService
 from app.api.v1.deps import get_current_user_id
 
 router = APIRouter()
@@ -10,6 +12,7 @@ router = APIRouter()
 
 class CreateOrderRequest(BaseModel):
     plan: str
+    pay_type: str = "jsapi"
 
 
 class PaymentCallbackRequest(BaseModel):
@@ -40,7 +43,7 @@ async def create_order(
 ):
     svc = PaymentService(db)
     try:
-        return await svc.create_order(user_id, data.plan)
+        return await svc.create_order(user_id, data.plan, data.pay_type)
     except ValueError as e:
         raise HTTPException(status_code=400, detail=str(e))
 
@@ -54,4 +57,32 @@ async def payment_callback(
     success = await svc.handle_payment_callback(data.payment_id, data.success)
     if not success:
         raise HTTPException(status_code=404, detail="Order not found")
-    return {"status": "ok"}
+    return {"status": "ok"}
+
+
+@router.post("/notify")
+async def wechat_pay_notify(request: Request, db: AsyncSession = Depends(get_db)):
+    body = await request.body()
+    body_str = body.decode("utf-8")
+    headers = dict(request.headers)
+
+    wxpay = WeChatPayService()
+    if not wxpay.verify_callback(headers, body_str):
+        raise HTTPException(status_code=401, detail="签名验证失败")
+
+    import json
+    data = json.loads(body_str)
+    resource = data.get("resource", {})
+    ciphertext = resource.get("ciphertext", "")
+    nonce = resource.get("nonce", "")
+    associated_data = resource.get("associated_data", "")
+
+    plaintext = wxpay.decrypt_callback(ciphertext, nonce, associated_data)
+    pay_data = json.loads(plaintext)
+    out_trade_no = pay_data.get("out_trade_no", "")
+    trade_state = pay_data.get("trade_state", "")
+
+    success = trade_state == "SUCCESS"
+    svc = PaymentService(db)
+    await svc.handle_payment_callback(out_trade_no, success)
+    return {"code": "SUCCESS", "message": "OK"}