Refactor and optimize templates and code structure

- Deleted outdated templates for epics, product brief, and requirements PRD.
- Introduced lazy loading for locale messages in i18n module to enhance performance.
- Updated main application bootstrap to parallelize CSRF token fetching and locale loading.
- Implemented code splitting for router configuration to optimize bundle size and loading times.
- Added WebSocket connection limits and rate limiting to improve server performance and prevent abuse.
- Enhanced input validation with compiled regex patterns for better performance and maintainability.

ccw/frontend/src/lib/i18n.ts

@@ -68,9 +68,21 @@ const messages: Record<Locale, Record<string, string>> = {
   zh: {},
 };
 
+/**
+ * Load messages for a specific locale only (lazy loading)
+ * This is the optimized init method that loads only the active locale
+ */
+export async function loadMessagesForLocale(locale: Locale): Promise<Record<string, string>> {
+  const localeMessages = await loadMessages(locale);
+  messages[locale] = localeMessages;
+  updateIntl(locale);
+  return localeMessages;
+}
+
 /**
  * Initialize translation messages for all locales
  * Call this during app initialization
+ * NOTE: Use loadMessagesForLocale() for faster single-locale init
  */
 export async function initMessages(): Promise<void> {
   // Load messages for both locales in parallel