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

src/lib/git.ts

@@ -14,6 +14,7 @@ import type {
   GitBranch,
   GitCommit,
   GitCommitComparison,
+  GitLfsStatus,
   GitRepositoryFile,
   GitRemote,
   MergeStrategy,
@@ -90,6 +91,35 @@ export function getStatus(path: string): Promise<GitStatus> {
   return invoke<GitStatus>("get_status", { path });
 }
 
+export function getGitLfsStatus(path: string): Promise<GitLfsStatus> {
+  return invoke<GitLfsStatus>("git_lfs_status", { path });
+}
+
+export function installGitLfs(path: string): Promise<GitLfsStatus> {
+  return invoke<GitLfsStatus>("git_lfs_install", { path });
+}
+
+export function trackGitLfsPattern(path: string, pattern: string, lockable = false): Promise<GitLfsStatus> {
+  return invoke<GitLfsStatus>("git_lfs_track", { path, pattern, lockable });
+}
+
+export function untrackGitLfsPattern(path: string, pattern: string): Promise<GitLfsStatus> {
+  return invoke<GitLfsStatus>("git_lfs_untrack", { path, pattern });
+}
+
+export function pullGitLfsObjects(path: string, remote?: string, username?: string, password?: string): Promise<GitLfsStatus> {
+  return invoke<GitLfsStatus>("git_lfs_pull", {
+    path,
+    remote: remote || null,
+    username: username ?? null,
+    password: password ?? null,
+  });
+}
+
+export function pruneGitLfsObjects(path: string): Promise<GitLfsStatus> {
+  return invoke<GitLfsStatus>("git_lfs_prune", { path });
+}
+
 // Sets the taskbar icon badge to ahead + behind + changed status files (0 clears it). Windows only — a no-op on
 // other platforms, since Windows has no native numeric badge to fall back to.
 export function setSyncBadge(ahead: number, behind: number, changes: number): Promise<void> {