feat: Add PDM support with auth & i18n enhancements (#627)

* feat: Add PDM support with auth & i18n enhancements

1. Added PDM project dependency management
   - Created pyproject.toml for dependency definitions
   - Added PDM lock file for reproducible builds
   - Created .pdm-python for virtual environment management

2. Enhanced authentication & configuration
   - Added user validation in base configuration
   - Implemented streamlit-authenticator for login functionality
   - Updated config.example.toml with user authentication fields

3. Improved internationalization (i18n)
   - Updated translation files for multiple languages (en, de, pt, vi, zh)
   - Enhanced i18n support in the web UI
   - Standardized translation structure across language files

config.example.toml

@@ -1,6 +1,15 @@
 [app]
 
     video_source = "pexels"  # "pexels" or "pixabay"
+
+    # 是否隐藏配置面板
+    # hide_config = false
+
+[user]
+    # 管理员用户名和密码，用于访问基础设置
+    username = "admin"
+    password = "admin"
+    email = "admin@example.com"  # 添加email字段，用于身份验证
     # Pexels API Key
     # Register at https://www.pexels.com/api/ to get your API key.
     # You can use multiple keys to avoid rate limits.