* fix: prefer project venv Python for patchers
* add: VM backup, restore, and switch support
Named backups via rsync --sparse for efficient sparse disk handling.
- vm_backup.sh: save current VM as a named backup to vm.backups/
- vm_restore.sh: restore a named backup into vm/
- vm_switch.sh: save current + restore target in one step
- Makefile targets: vm_backup, vm_restore, vm_switch, vm_list
- Documentation added to all READMEs (EN, ZH, KO, JA)
Closes#204
Made-with: Cursor
