iso: fix installer autostart (root uses zsh) + TANINUX branding

- /root/.zprofile launches tanin-installer on tty1 (root shell is zsh, so
  .bash_profile was ignored); striplive removes .zprofile on the target
- profiledef: MERGE releng's file_permissions (lost .automated_script.sh +x ->
  the 'permission denied' message) + keep our entries
- branding: TANINUX os-release/hostname/motd; bootstrap rebrands the boot menus

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

iso/overrides/airootfs/etc/calamares/modules/shellprocess-striplive.conf

@@ -6,6 +6,6 @@ timeout: 30
 script:
 - "rm -f /etc/systemd/system/getty@tty1.service.d/autologin.conf"
 - "rmdir --ignore-fail-on-non-empty /etc/systemd/system/getty@tty1.service.d 2>/dev/null || true"
-- "rm -f /root/.bash_profile"
+- "rm -f /root/.zprofile"
 - "rm -f /usr/local/bin/tanin-installer"
 - "systemctl set-default graphical.target"