chore: 添加虚拟环境到仓库

- 添加 backend_service/venv 虚拟环境
- 包含所有Python依赖包
- 注意：虚拟环境约393MB，包含12655个文件

backend_service/venv/lib/python3.13/site-packages/posthog/poller.py

@@ -0,0 +1,20 @@
+import threading
+
+
+class Poller(threading.Thread):
+    def __init__(self, interval, execute, *args, **kwargs):
+        threading.Thread.__init__(self)
+        self.daemon = True  # Make daemon to not interfere with program exit
+        self.stopped = threading.Event()
+        self.interval = interval
+        self.execute = execute
+        self.args = args
+        self.kwargs = kwargs
+
+    def stop(self):
+        self.stopped.set()
+        self.join()
+
+    def run(self):
+        while not self.stopped.wait(self.interval.total_seconds()):
+            self.execute(*self.args, **self.kwargs)