Initial commit: Python library for Markdown note services

- Add MDAuth class for authentication and session management
- Add MDClient class for note operations (CRUD + export/search)
- Add CLI tool mdclient_cli.py for quick operations
- Support for CodiMD, HedgeDoc, and HackMD services
- Multi-endpoint API compatibility

Co-Authored-By: Claude Sonnet 4 <noreply@anthropic.com>

.env.example

@@ -0,0 +1,12 @@
+# MDclient 設定檔案範例
+# 複製此檔案為 .env 並填入你的資訊
+
+# 伺服器位址
+MDCLIENT_URL=https://codimd.lotimmy.com
+
+# 登入帳密
+MDCLIENT_EMAIL=your@email.com
+MDCLIENT_PASSWORD=your_password
+
+# Cookie 檔案路徑（可選，預設為 key.conf）
+# MDCLIENT_COOKIE_FILE=key.conf