Edit autostart, startup order and tags from the info screen

The info screen's Resources table shows Autostart (yes/no), Startup
(order, up and down delays) and Tags. o opens a dialog to change them.
Only keys that differ are sent, in one `set <kind> config` call
through the existing set_net. A confirm lists the old and new value
of each key.

Tags are removed with `--delete tags` on set config. The CLI also has
a `delete ct|vm ... tags` command, but it shares the form that
destroys the whole guest, so the app never uses it; nothing in the
code builds a delete ct|vm argv. Inputs are validated before sending:
startup values must be ints >= 0, and tags must match
[A-Za-z0-9_][A-Za-z0-9_+.-]*. They are split on ; , or whitespace and
deduplicated.

Live test on CT 104: onboot 1 -> 0, startup order=5,up=10, tag
tui-test added, then all set back through the dialog. The config
ended identical to the baseline.

Closes #18

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

README.md

@@ -44,6 +44,7 @@ uv run cv4pve-tui
 | `Enter` then `e` | in info: edit cores / memory / grow a disk (disk growth asks again; it cannot be undone) |
 | `Enter` then `b` | in info: backup now (snapshot, zstd, storage choice); `a` there = also show backups of earlier guests that had the same VMID |
 | `Enter` then `n` | in info: edit network (bridge, VLAN, firewall, IPv4/IPv6; VM IP via cloud-init at next boot); `u` there = undo the last network change of this guest (this session only) |
+| `Enter` then `o` | in info: edit autostart, startup order (order, up and down delay) and tags (one confirmed `set config` call; empty fields remove the setting) |
 | `Enter` then `p` / `R` / `D` | in info: take a snapshot (name, description, VM: include RAM) / roll back to the snapshot under the cursor (confirms; starts the guest again if it is running) / delete the snapshot under the cursor (confirms) |
 | `t` | shell in a running LXC container (`ssh -t root@<node> pct enter <vmid>`) |
 | `l` | tasks: recent cluster tasks (start, duration, node, type, VMID, user, status; `!` marks failures); `Enter` shows the log of the task under the cursor, `g` reloads. In info: `l` = only this guest's tasks |