fix: make basePath configurable via NEXT_PUBLIC_BASE_PATH env var

Enables platform-agnostic deployment — GitHub Pages sets the env var
in CI, while Vercel/Netlify/local dev default to root path.

.github/workflows/deploy.yml

@@ -28,6 +28,8 @@ jobs:
       - run: npm ci
 
       - run: npm run build
+        env:
+          NEXT_PUBLIC_BASE_PATH: /loldle
 
       - uses: actions/upload-pages-artifact@v3
         with: