Bake Sunshine remote admin + add one-command configured ISO builder

- Sunshine flatpak in first-boot list; autostarts with the console
  account's session (bc250-sunshine-autostart, honors CONSOLE_KID_USER)
- bc250-personalize: one-shot display names from /etc/bc250-console.conf
- build-console.sh + console.env(.example): fill in usernames/passwords/
  display names, get a fully personalized ISO — no post-install steps
  beyond per-account logins. Generated files git-ignored (credentials)
- Docs: Moonlight is the remote-admin path; RDP marked blocked by the
  mutter cursor-metadata screencast crash on GFX1013

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

files/console/usr/lib/systemd/system/bc250-personalize.service

@@ -0,0 +1,10 @@
+[Unit]
+Description=One-time console account personalization (display names)
+ConditionPathExists=!/var/lib/bc250/.personalized
+
+[Service]
+Type=oneshot
+ExecStart=/usr/bin/bc250-personalize
+
+[Install]
+WantedBy=multi-user.target