use a fixed ssh port

[marcoieni]

To migrate, temporarily add this to the justfile and run this task:

# Migrate an existing VM to the fixed SSH port in buddy.yaml, preserving its disk.
# This restarts the VM and interrupts running guest processes.
fix-ssh:
    limactl stop "{{ vm }}"
    limactl edit --tty=false --ssh-port 49335 "{{ vm }}"
    limactl start --progress "{{ vm }}"