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

webui/i18n/en.json

@@ -1,6 +1,14 @@
 {
   "Language": "English",
   "Translation": {
+    "Login Required": "Login Required",
+    "Please login to access settings": "Please login to access settings",
+    "Username": "Username",
+    "Password": "Password",
+    "Login": "Login",
+    "Login Error": "Login Error",
+    "Incorrect username or password": "Incorrect username or password",
+    "Please enter your username and password": "Please enter your username and password",
     "Video Script Settings": "**Video Script Settings**",
     "Video Subject": "Video Subject (Provide a keyword, :red[AI will automatically generate] video script)",
     "Script Language": "Language for Generating Video Script (AI will automatically output based on the language of your subject)",
@@ -16,7 +24,7 @@
     "Video Concat Mode": "Video Concatenation Mode",
     "Random": "Random Concatenation (Recommended)",
     "Sequential": "Sequential Concatenation",
-    "Video Transition Mode": "Video Transition Mode", 
+    "Video Transition Mode": "Video Transition Mode",
     "None": "None",
     "Shuffle": "Shuffle",
     "FadeIn": "FadeIn",