feat(client): 添加 Python 客户端及示例应用

- 新增 python-client 模块，提供 ConfigClient 配置拉取、定时同步、变更监听
- 使用 pyaes 替代 cryptography 实现 AES 解密，避免编译问题
- 新增 python-client-demo Flask 示例应用
- .gitignore 添加 Python 相关忽略规则

python-client/kenaito_conf/config.py

@@ -0,0 +1,20 @@
+class Config:
+    def __init__(
+        self,
+        base_url: str = "",
+        app_name: str = "",
+        env: str = "dev",
+        version: str = "latest",
+        token: str = "",
+        sync_interval: int = 60,
+        ignore_global: bool = False,
+        cache_dir: str = ".",
+    ):
+        self.base_url = base_url
+        self.app_name = app_name
+        self.env = env
+        self.version = version
+        self.token = token
+        self.sync_interval = sync_interval
+        self.ignore_global = ignore_global
+        self.cache_dir = cache_dir