feat: 实现清理失效账号安全方案（包含预览、SSE测试、安全删除以及本地标记清空）

backend/app/services/website_client.py

@@ -345,7 +345,7 @@ class Sub2ApiWebsiteClient:
 
     def account_exists(self, account_id: str, endpoint: str = "/accounts") -> bool | None:
         """检查目标账号是否存在。
-        
+
         优先拉取账号列表判断：
         - 列表成功取到 → return account_id in ids（True=存在，False=已删除）
         - 列表取不到（None）→ return None（校验失败，不清本地）
@@ -357,6 +357,82 @@ class Sub2ApiWebsiteClient:
             return None
         return account_id in ids
 
+    def test_account(self, account_id: str, endpoint: str = "/accounts") -> dict[str, Any]:
+        """测试远端账号可用性。利用 SSE 监听 test_complete 事件的 success 状态。
+        若 404，返回 {"status": "404", "cleanup_allowed": True, "message": "账号不存在"}
+        若 timeout / 无法建立连接，返回 {"status": "timeout"/"error", "cleanup_allowed": False}
+        """
+        import json
+        url = self._url(f"{endpoint}/{account_id}/test")
+        headers = self._headers()
+        # Accept text/event-stream since it's an SSE stream
+        headers["Accept"] = "text/event-stream"
+
+        try:
+            with self._client.stream("POST", url, headers=headers) as response:
+                if response.status_code == 404:
+                    return {"status": "404", "cleanup_allowed": True, "message": "账号在远端不存在 (404)"}
+                if response.status_code >= 400:
+                    return {"status": "http_error", "cleanup_allowed": False, "message": f"测试接口返回 HTTP {response.status_code}"}
+
+                # Read SSE stream line by line
+                current_event = None
+                success_value = None
+                has_error_event = False
+
+                for line in response.iter_lines():
+                    if not line:
+                        continue
+                    if line.startswith("event:"):
+                        current_event = line[6:].strip()
+                    elif line.startswith("data:"):
+                        data_str = line[5:].strip()
+                        if current_event == "error":
+                            has_error_event = True
+                        if current_event == "test_complete" or not current_event:
+                            try:
+                                parsed = json.loads(data_str)
+                                if isinstance(parsed, dict):
+                                    if "success" in parsed:
+                                        success_value = parsed["success"]
+                                    elif parsed.get("event") == "test_complete" and "success" in parsed:
+                                        success_value = parsed["success"]
+                            except Exception:
+                                pass
+
+                if success_value is True:
+                    return {"status": "success", "cleanup_allowed": False, "message": "测试成功，账号有效"}
+                elif success_value is False:
+                    return {"status": "failed", "cleanup_allowed": True, "message": "测试失败，账号失效"}
+                elif has_error_event:
+                    return {"status": "error", "cleanup_allowed": False, "message": "测试接口返回了错误事件"}
+                else:
+                    return {"status": "invalid_sse", "cleanup_allowed": False, "message": "未收到有效的测试完成事件"}
+
+        except httpx.TimeoutException as exc:
+            return {"status": "timeout", "cleanup_allowed": False, "message": f"连接超时: {exc}"}
+        except Exception as exc:
+            return {"status": "error", "cleanup_allowed": False, "message": f"请求异常: {exc}"}
+
+    def delete_account(self, account_id: str, endpoint: str = "/accounts") -> dict[str, Any]:
+        """删除目标账号。
+        若 404 视为 already_deleted。
+        """
+        url = self._url(f"{endpoint}/{account_id}")
+        headers = self._headers()
+        try:
+            resp = self._client.request("DELETE", url, headers=headers)
+            if resp.status_code == 404:
+                return {"status": "already_deleted", "message": "账号不存在或已在远端被删除"}
+            resp.raise_for_status()
+            return {"status": "deleted", "message": "账号已删除"}
+        except httpx.HTTPStatusError as exc:
+            if exc.response.status_code == 404:
+                return {"status": "already_deleted", "message": "账号不存在或已在远端被删除"}
+            raise WebsiteError(_friendly_http_error(exc)) from exc
+        except Exception as exc:
+            raise WebsiteError(f"删除账号失败: {exc}") from exc
+
     @staticmethod
     def extract_id(value: Any) -> str:
         return _extract_id(value)