Add Textual TUI for managing Proxmox guests via cv4pve-cli

List VMs and LXC containers from the current cv4pve-cli context and
start, shutdown, stop and reboot them, change cores and memory, and
grow disks. The app shells out to `cv4pve-cli -o json` and stores no
credentials.

- Every mutating call uses --wait: without it cv4pve-cli exits 0 even
  when the task fails.
- shutdown, stop and reboot need confirmation; disk growth is
  increment-only and asks again because it cannot be undone.
- After an action the acted-on guest's status is read from
  status/current, because /cluster/resources lags a few seconds.
- Notifies when a cores/memory change is pending until reboot.

Tests mock cv4pve-cli (85 tests). Live-tested edit, shutdown, start
and reboot on CT 104 (mainframe), restored afterwards; disk resize
was not run live.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/cv4pve_tui/__init__.py

@@ -0,0 +1 @@
+"""Textual TUI for cv4pve-cli."""