接入微信一键登录服务端接口

改动内容：新增微信 code 换 openid 集成、/api/v1/auth/wechat-login 登录接口、微信用户创建/复用逻辑和测试覆盖。

验证方式：python -m pytest tests\\test_auth.py tests\\test_health.py -q 通过。

app/api/v1/auth.py

@@ -2,6 +2,7 @@
 
 路由前缀 `/api/v1/auth`,包含:
   POST /jverify-login         极光一键登录(loginToken → 手机号 → 注册即登录 → 签 JWT)
+  POST /wechat-login          微信 App 授权登录(code → openid → 注册即登录 → 签 JWT)
   POST /sms/send              发短信验证码(mock 阶段任意 6 位通过)
   POST /sms/login             手机号 + 验证码登录
   POST /refresh               用 refresh_token 换新的 token 对
@@ -20,6 +21,7 @@ from app.core.ratelimit import enforce_rate_limit, rate_limit
 from app.core.security import TokenError, decode_token, issue_token_pair
 from app.integrations.jiguang import JiguangError, mask_phone, verify_and_get_phone
 from app.integrations.sms import SmsError, send_code, verify_code
+from app.integrations.wechat_login import WechatLoginError, code_to_userinfo
 from app.repositories import onboarding as onboarding_repo
 from app.repositories import user as user_repo
 from app.schemas.auth import (
@@ -32,6 +34,7 @@ from app.schemas.auth import (
     TokenPair,
     TokenWithUser,
     UserOut,
+    WechatLoginRequest,
 )
 
 logger = logging.getLogger("shagua.auth")
@@ -84,6 +87,35 @@ def jverify_login(req: JverifyLoginRequest, db: DbSession) -> TokenWithUser:
     return _login_response(user, onboarding_completed=completed)
 
 
+# ===================== 微信 App 登录 =====================
+
+@router.post(
+    "/wechat-login",
+    response_model=TokenWithUser,
+    summary="微信一键登录",
+    dependencies=[Depends(rate_limit(20, 60, "wechat-login"))],
+)
+def wechat_login(req: WechatLoginRequest, db: DbSession) -> TokenWithUser:
+    try:
+        info = code_to_userinfo(req.code)
+    except WechatLoginError as e:
+        logger.error("[WECHAT] login code exchange failed: %s", e, exc_info=True)
+        raise HTTPException(status_code=502, detail=str(e)) from e
+
+    user = user_repo.upsert_user_for_wechat_login(
+        db,
+        openid=info["openid"],
+        nickname=info.get("nickname"),
+        avatar_url=info.get("avatar_url"),
+    )
+    if user.status != "active":
+        raise HTTPException(status_code=403, detail="account disabled")
+
+    completed = onboarding_repo.is_completed(db, user_id=user.id, device_id=req.device_id)
+    logger.info("wechat_login ok user_id=%d onboarded=%s", user.id, completed)
+    return _login_response(user, onboarding_completed=completed)
+
+
 # ===================== 短信登录 =====================
 
 @router.post(