Host [tanin] on Gitea Arch registry (9 pkgs, public)

- publish-tanin-repo.sh: upload built packages to the Gitea Arch registry
- distro/tanin.pacman.conf: the [tanin] pacman.conf snippet
- manifest: [tanin] is LIVE at git.openbureau.ch/api/packages/karim/arch/tanin

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

distro/tanin.pacman.conf

@@ -0,0 +1,6 @@
+# [tanin] — TANINUX (camel) binary repo, hosted on the Gitea Arch registry.
+# Append this block to /etc/pacman.conf, then:  sudo pacman -Sy
+#   sudo pacman -S tanin-desktop      # pulls the whole niri/eww desktop
+[tanin]
+SigLevel = Optional TrustAll
+Server = https://git.openbureau.ch/api/packages/karim/arch/tanin/$arch