Capture omarchy-air's post-10-16 customizations into its layer

Everything on the Air that existed only on the machine:

- git/config and mimeapps.list, which the omarchy-air-host branch captured
  but profiles never picked up.
- NetBird: netbird-bin under [aur], the networkd drop-in it writes, and a
  setup.sh that runs `netbird service install` and enables the unit (the AUR
  package ships none). `netbird up` stays manual.
- ufw rules beyond Omarchy's stock set and the handoff step's 4242 rule:
  ssh and the ocovo fabric (7746/udp) from the home LAN, 7746 over wt0, and
  7790/tcp.

base gains omarchy-fix-qt-color and a setup.sh that runs it. Qt 6.12's
QtQuick Color singleton shadows the shell's qs.Commons Color, so the bar,
lock screen and polkit dialog lose every colour; the fix renames the
singleton to ShellColor. An omarchy upgrade restores the stock files, so it
is idempotent, skips Qt < 6.12, and no-ops once upstream renames it.
Verified: run against the pristine backup it reproduces the Air's
hand-patched /usr/share/omarchy/shell byte for byte.

Left out on purpose: ocovo-node.service (written by `ocovo service
install`) and environment.d/ohv.conf belong to those projects.

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

profiles/machines/macbook-air-m2/system/systemd/networkd.conf.d/99-netbird.conf

@@ -0,0 +1,6 @@
+# Created by NetBird to prevent systemd-networkd from removing
+# routes and policy rules managed by NetBird.
+
+[Network]
+ManageForeignRoutes=no
+ManageForeignRoutingPolicyRules=no