重构为 HTTP SSO 扫码方案并引入 Vue3 前端

移除 Playwright 浏览器自动化，改用 passport/SSO HTTP 接口获取二维码与轮询登录；后端模块化拆分，前端替换为 Vue3 SPA。

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/session.py

@@ -0,0 +1,30 @@
+import threading
+
+
+class LoginSession:
+    """全局单例登录会话（一次仅支持一个扫码流程）"""
+
+    def __init__(self):
+        self.session_id = None
+        self.sso_client = None
+        self.status = "idle"
+        self.cookies = None
+        self.message = ""
+        self.start_time = 0
+        self.proxy_used = None
+        self.nickname = None
+        self.login_timeout = 600
+        self.lock = threading.Lock()
+
+    def reset(self):
+        self.session_id = None
+        self.sso_client = None
+        self.cookies = None
+        self.nickname = None
+        self.start_time = 0
+        self.proxy_used = None
+        self.status = "idle"
+        self.message = ""
+
+
+login_session = LoginSession()