feat(tauri): migrate from GitLite to Gitty and clean up legacy data

This commit updates the installer and configuration to transition from
GitLite to Gitty. It includes macros for migrating legacy data and
uninstalling the previous GitLite installation, ensuring a smoother
upgrade experience for users.

- Added migration and uninstallation macros for legacy GitLite data
- Updated application identifier from com.git-lite to com.gitty
- Enhanced post-installation cleanup for legacy shortcuts

src-tauri/tauri.conf.json

@@ -2,7 +2,7 @@
   "$schema": "https://schema.tauri.app/config/2",
   "productName": "Gitty",
   "version": "2026.7.16",
-  "identifier": "com.git-lite",
+  "identifier": "com.gitty",
   "build": {
     "beforeDevCommand": "npm run dev",
     "devUrl": "http://127.0.0.1:1420",