feat(git-lfs): add Git LFS status and sidecar bundling

Adds Git LFS support to the backend API and related UI.
The app now exposes commands to inspect, install, track and pull.
A sidecar git-lfs binary is bundled and a prep script is added.
This prepares the correct binary for each target platform.

- Expose Git LFS status and management commands in API
- Bundle and prepare a sidecar git-lfs binary for targets
- Update packaging, docs, and README with LFS notes

package.json

@@ -6,6 +6,7 @@
   "scripts": {
     "dev": "vite --host 127.0.0.1",
     "build": "vite build",
+    "prepare:lfs": "node scripts/prepare-git-lfs-sidecar.mjs",
     "icons": "node scripts/generate-app-icons.mjs",
     "preview": "vite preview --host 127.0.0.1",
     "tauri": "tauri",