fix: use correct cursor package (code-cursor) and clean up manual installation

- Replace cursor-cli with code-cursor package (the correct Nix package)
- Remove manually installed Cursor.app from /Applications/
- Remove broken symlink from /usr/local/bin/cursor
- Backup Cursor user data to ~/dotfiles/backups/cursor/
- Nix-managed cursor (v1.5.11) now working correctly from /run/current-system/sw/bin/cursor

nixos/hosts/macos.nix

@@ -64,7 +64,7 @@
     cowsay
     lolcat
     alacritty
-    cursor-cli
+    code-cursor
     tree
   ];