feat(auth): M2 conflict_ticket 令牌(编码已验证 openid+phone)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/core/security.py

@@ -126,6 +126,52 @@ def decode_bind_ticket(token: str) -> dict[str, Any]:
     return {"openid": payload["sub"], "wnk": payload.get("wnk"), "wav": payload.get("wav")}
 
 
+def create_conflict_ticket(
+    *, openid: str, wechat_nickname: str | None, wechat_avatar_url: str | None, phone: str
+) -> str:
+    """手机号占用时签发的短时"冲突处理"令牌。
+
+    比 bind_ticket 多编码 **已验证的手机号 phone** —— 换绑/继续绑定只认它,证明"这对
+    openid/手机号刚在绑号时验证通过",免用户重输验证码,又堵住"拿自己 openid + 任意手机号
+    去夺号"的接管漏洞。typ='wechat_conflict';有效期复用 WECHAT_BIND_TICKET_EXPIRE_MINUTES。
+    """
+    now = _now()
+    expire = now + timedelta(minutes=settings.WECHAT_BIND_TICKET_EXPIRE_MINUTES)
+    payload: dict[str, Any] = {
+        "sub": openid,
+        "typ": "wechat_conflict",
+        "wnk": wechat_nickname,
+        "wav": wechat_avatar_url,
+        "phn": phone,
+        "iat": int(now.timestamp()),
+        "exp": int(expire.timestamp()),
+    }
+    return jwt.encode(payload, settings.JWT_SECRET_KEY, algorithm=settings.JWT_ALGORITHM)
+
+
+def decode_conflict_ticket(token: str) -> dict[str, Any]:
+    """解析"冲突处理"令牌,校验签名/过期/类型。失败抛 TokenError。
+
+    返回 {'openid': str, 'wnk': str|None, 'wav': str|None, 'phone': str}。
+    """
+    try:
+        payload = jwt.decode(token, settings.JWT_SECRET_KEY, algorithms=[settings.JWT_ALGORITHM])
+    except jwt.ExpiredSignatureError as e:
+        raise TokenError("conflict ticket expired") from e
+    except jwt.InvalidTokenError as e:
+        raise TokenError(f"invalid conflict ticket: {e}") from e
+    if payload.get("typ") != "wechat_conflict":
+        raise TokenError(f"wrong token type: want=wechat_conflict got={payload.get('typ')}")
+    if "sub" not in payload or "phn" not in payload:
+        raise TokenError("conflict ticket missing sub/phn")
+    return {
+        "openid": payload["sub"],
+        "wnk": payload.get("wnk"),
+        "wav": payload.get("wav"),
+        "phone": payload["phn"],
+    }
+
+
 # ===================== 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。