Add Chinese (Simplified and Traditional) localization files and implement i18n tests

- Created zh-CN.json and zh-TW.json for Simplified and Traditional Chinese translations respectively.
- Added comprehensive test suite in test_i18n.py to validate JSON structure, server-side i18n functionality, and translation completeness across multiple languages.

standalone.py

@@ -339,6 +339,11 @@ class StandaloneLoraManager(LoraManager):
                     logger.warning(f"Failed to add static route on initialization for {target_path}: {e}")
                     continue
         
+        # Add static route for locales JSON files
+        if os.path.exists(config.i18n_path):
+            app.router.add_static('/locales', config.i18n_path)
+            logger.info(f"Added static route for locales: /locales -> {config.i18n_path}")
+            
         # Add static route for plugin assets
         app.router.add_static('/loras_static', config.static_path)