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/crypto.py

@@ -0,0 +1,29 @@
+import base64
+import hashlib
+
+import pyaes
+
+CRYPT_PREFIX = "{Cipher}"
+
+
+def decrypt_config(secret: str, data: str) -> str:
+    if not data.startswith(CRYPT_PREFIX):
+        return data
+    encrypted = data[len(CRYPT_PREFIX):]
+    return decrypt_with_aes(secret, encrypted)
+
+
+def decrypt_with_aes(key: str, data: str) -> str:
+    md5_hash = hashlib.md5(key.encode()).hexdigest()
+    aes_key = md5_hash[16:].encode()
+
+    cipher_text = base64.b64decode(data)
+
+    iv = b"\0" * 16
+    aes_cbc = pyaes.AESModeOfOperationCBC(aes_key, iv=iv)
+    plain_text = aes_cbc.decrypt(cipher_text)
+
+    padding = plain_text[-1]
+    plain_text = plain_text[:-padding]
+
+    return plain_text.decode()