➕(frontend) install vite-plugin-static-copy for MediaPipe WASM assets

Add vite-plugin-static-copy as a dependency. It will be used to copy
and serve the WASM modules shipped by the MediaPipe JS dependency
from the frontend build output.

src/frontend/package.json

@@ -70,6 +70,7 @@
     "typescript": "6.0.3",
     "typescript-eslint": "8.60.1",
     "vite": "8.0.14",
+    "vite-plugin-static-copy": "4.1.1",
     "vite-plugin-svgr": "5.2.0"
   }
 }