feat: Add HTTPS/Traefik support with centralized endpoints

- Create traefik/agent-ui.yml with full routing config for domain z590.nucleoriofrio.com
- Add frontend/src/config/endpoints.ts for automatic HTTP/HTTPS detection
- Update all hardcoded localhost URLs to use relative paths
- WebSocket connections auto-detect wss:// vs ws:// based on page protocol
- Configure path-based WebSocket routing (/ws/terminal, /ws/mcp, /ws/status, /ws/whisper)
- Add commented IP whitelist middleware for future security

frontend/src/stores/theme.ts

@@ -44,7 +44,8 @@ export interface DesignTokens {
   examples: Record<string, string>
 }
 
-const API_URL = 'http://localhost:4101'
+// Uses relative URLs - works with Vite proxy in dev and Traefik in production
+const API_URL = ''
 
 // =====================
 // Store