feat(i18n): Implement server-side internationalization support

- Added ServerI18nManager to handle translations and locale settings on the server.
- Integrated server-side translations into templates, reducing language flashing on initial load.
- Created API endpoints for setting and getting user language preferences.
- Enhanced client-side i18n handling to work seamlessly with server-rendered content.
- Updated various templates to utilize the new translation system.
- Added mixed i18n handler to coordinate server and client translations, improving user experience.
- Expanded translation files to include initialization messages for various components.

py/services/server_i18n.py

@@ -0,0 +1,154 @@
+import os
+import json
+import logging
+from typing import Dict, Any, Optional
+
+logger = logging.getLogger(__name__)
+
+class ServerI18nManager:
+    """Server-side internationalization manager for template rendering"""
+    
+    def __init__(self):
+        self.translations = {}
+        self.current_locale = 'en'
+        self._load_translations()
+    
+    def _load_translations(self):
+        """Load all translation files from the static/js/i18n directory"""
+        i18n_path = os.path.join(
+            os.path.dirname(os.path.dirname(os.path.dirname(__file__))), 
+            'static', 'js', 'i18n', 'locales'
+        )
+        
+        if not os.path.exists(i18n_path):
+            logger.warning(f"I18n directory not found: {i18n_path}")
+            return
+        
+        # Load all available locale files
+        for filename in os.listdir(i18n_path):
+            if filename.endswith('.js'):
+                locale_code = filename[:-3]  # Remove .js extension
+                try:
+                    self._load_locale_file(i18n_path, filename, locale_code)
+                except Exception as e:
+                    logger.error(f"Error loading locale file {filename}: {e}")
+    
+    def _load_locale_file(self, path: str, filename: str, locale_code: str):
+        """Load a single locale file and extract translation data"""
+        file_path = os.path.join(path, filename)
+        
+        try:
+            with open(file_path, 'r', encoding='utf-8') as f:
+                content = f.read()
+                
+            # Look for export const pattern like: export const en = { ... }
+            import re
+            
+            # Extract the variable name and object
+            export_pattern = r'export\s+const\s+(\w+)\s*=\s*(\{.*\});?\s*$'
+            match = re.search(export_pattern, content, re.DOTALL | re.MULTILINE)
+            
+            if not match:
+                logger.warning(f"No export const found in {filename}")
+                return
+            
+            var_name = match.group(1)
+            js_object = match.group(2)
+            
+            # Convert JS object to JSON
+            json_str = self._js_object_to_json(js_object)
+            
+            # Parse as JSON
+            translations = json.loads(json_str)
+            self.translations[locale_code] = translations
+            
+            logger.debug(f"Loaded translations for {locale_code} (variable: {var_name})")
+            
+        except Exception as e:
+            logger.error(f"Error parsing locale file {filename}: {e}")
+    
+    def _js_object_to_json(self, js_obj: str) -> str:
+        """Convert JavaScript object to JSON string"""
+        import re
+        
+        # Remove comments (single line and multi-line)
+        js_obj = re.sub(r'//.*?$', '', js_obj, flags=re.MULTILINE)
+        js_obj = re.sub(r'/\*.*?\*/', '', js_obj, flags=re.DOTALL)
+        
+        # Replace unquoted object keys with quoted keys
+        js_obj = re.sub(r'(\s*)([a-zA-Z_$][a-zA-Z0-9_$]*)\s*:', r'\1"\2":', js_obj)
+        
+        # Handle strings more robustly using regex
+        # First, find all single-quoted strings and replace them with double-quoted ones
+        def replace_single_quotes(match):
+            content = match.group(1)
+            # Escape any double quotes in the content
+            content = content.replace('"', '\\"')
+            # Handle escaped single quotes
+            content = content.replace("\\'", "'")
+            return f'"{content}"'
+        
+        # Replace single-quoted strings with double-quoted strings
+        js_obj = re.sub(r"'([^'\\]*(?:\\.[^'\\]*)*)'", replace_single_quotes, js_obj)
+        
+        return js_obj
+    
+    def set_locale(self, locale: str):
+        """Set the current locale"""
+        if locale in self.translations:
+            self.current_locale = locale
+        else:
+            logger.warning(f"Locale {locale} not found, using 'en'")
+            self.current_locale = 'en'
+    
+    def get_translation(self, key: str, params: Dict[str, Any] = None) -> str:
+        """Get translation for a key with optional parameters"""
+        if self.current_locale not in self.translations:
+            return key
+        
+        # Navigate through nested object using dot notation
+        keys = key.split('.')
+        value = self.translations[self.current_locale]
+        
+        for k in keys:
+            if isinstance(value, dict) and k in value:
+                value = value[k]
+            else:
+                # Fallback to English if current locale doesn't have the key
+                if self.current_locale != 'en' and 'en' in self.translations:
+                    en_value = self.translations['en']
+                    for k in keys:
+                        if isinstance(en_value, dict) and k in en_value:
+                            en_value = en_value[k]
+                        else:
+                            return key
+                    value = en_value
+                else:
+                    return key
+                break
+        
+        if not isinstance(value, str):
+            return key
+        
+        # Replace parameters if provided
+        if params:
+            for param_key, param_value in params.items():
+                placeholder = f"{{{param_key}}}"
+                double_placeholder = f"{{{{{param_key}}}}}"
+                value = value.replace(placeholder, str(param_value))
+                value = value.replace(double_placeholder, str(param_value))
+        
+        return value
+    
+    def get_available_locales(self) -> list:
+        """Get list of available locales"""
+        return list(self.translations.keys())
+    
+    def create_template_filter(self):
+        """Create a Jinja2 filter function for templates"""
+        def t_filter(key: str, **params) -> str:
+            return self.get_translation(key, params)
+        return t_filter
+
+# Create global instance
+server_i18n = ServerI18nManager()