Fix: Use relative URLs for API endpoints in Hugging Face environment

frontend/src/config/api.js

@@ -1,5 +1,5 @@
 // src/config/api.js
-export const API_LLM = import.meta.env.VITE_API_URL_LLM || 'http://localhost:7860/api/llm/generate';
-export const API_TTS = import.meta.env.VITE_API_URL_TTS || 'http://localhost:7860/api/tts/generate-tts';
-export const API_STT = import.meta.env.VITE_API_URL_STT || 'http://localhost:7860/api/stt/transcribe';
+export const API_LLM = import.meta.env.VITE_API_URL_LLM || '/api/llm/generate';
+export const API_TTS = import.meta.env.VITE_API_URL_TTS || '/api/tts/generate-tts';
+export const API_STT = import.meta.env.VITE_API_URL_STT || '/api/stt/transcribe';
 export const WS_URL  = import.meta.env.VITE_WS_URL || 'ws://localhost:7860/ws';