refactor(config): use Vite proxy for API requests and change backend port

- Configure Vite dev server to proxy /v1 requests to backend
- Change backend port from 8000 to 8001
- Simplify API URLs to relative paths instead of absolute localhost URLs
- Increase debounce delay from 500ms to 1000ms for better stability
- Update README documentation to reflect all changes

src/utils/config.js

@@ -1,18 +1,3 @@
 export const DEBUG = import.meta.env.DEV
-export const API_URL = import.meta.env.VITE_API_URL || 'http://localhost:8000/v1/completions'
-
-const buildDefaultOcrUrl = (apiUrl) => {
-  if (typeof window === 'undefined') {
-    return 'http://localhost:8000/v1/ocr'
-  }
-
-  try {
-    const url = new URL(apiUrl, window.location.origin)
-    url.pathname = '/v1/ocr'
-    return url.toString()
-  } catch {
-    return 'http://localhost:8000/v1/ocr'
-  }
-}
-
-export const OCR_URL = import.meta.env.VITE_OCR_URL || buildDefaultOcrUrl(API_URL)
+export const API_URL = import.meta.env.VITE_API_URL || '/v1/completions'
+export const OCR_URL = import.meta.env.VITE_OCR_URL || '/v1/ocr'