feat(auth): 微信登录 bind_ticket 令牌 + 配置

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/core/security.py

@@ -87,6 +87,45 @@ def issue_token_pair(user_id: int) -> dict[str, Any]:
     }
 
 
+def create_bind_ticket(
+    *, openid: str, wechat_nickname: str | None, wechat_avatar_url: str | None
+) -> str:
+    """微信登录未命中 openid 时,签发短时"待绑手机"令牌,承载 openid + 微信昵称头像。
+
+    typ='wechat_bind'、sub=openid;有效期 settings.WECHAT_BIND_TICKET_EXPIRE_MINUTES 分钟。
+    与 access/refresh 用同一 JWT_SECRET_KEY 签名,靠 typ 区分,decode_bind_ticket 校验 typ。
+    """
+    now = _now()
+    expire = now + timedelta(minutes=settings.WECHAT_BIND_TICKET_EXPIRE_MINUTES)
+    payload: dict[str, Any] = {
+        "sub": openid,
+        "typ": "wechat_bind",
+        "wnk": wechat_nickname,
+        "wav": wechat_avatar_url,
+        "iat": int(now.timestamp()),
+        "exp": int(expire.timestamp()),
+    }
+    return jwt.encode(payload, settings.JWT_SECRET_KEY, algorithm=settings.JWT_ALGORITHM)
+
+
+def decode_bind_ticket(token: str) -> dict[str, Any]:
+    """解析"待绑手机"令牌,校验签名/过期/类型。失败抛 TokenError。
+
+    返回 {'openid': str, 'wnk': str|None, 'wav': str|None}。
+    """
+    try:
+        payload = jwt.decode(token, settings.JWT_SECRET_KEY, algorithms=[settings.JWT_ALGORITHM])
+    except jwt.ExpiredSignatureError as e:
+        raise TokenError("bind ticket expired") from e
+    except jwt.InvalidTokenError as e:
+        raise TokenError(f"invalid bind ticket: {e}") from e
+    if payload.get("typ") != "wechat_bind":
+        raise TokenError(f"wrong token type: want=wechat_bind got={payload.get('typ')}")
+    if "sub" not in payload:
+        raise TokenError("bind ticket missing sub")
+    return {"openid": payload["sub"], "wnk": payload.get("wnk"), "wav": payload.get("wav")}
+
+
 # ===================== 密码 hash(admin 后台账号用)=====================
 # 用户侧是手机号+验证码登录,不存密码;仅 admin 账号用 username+password 登录。