Initial commit — TANINUX (camel): management app + distro packaging

- app: GTK System Settings (tsettings) + Software Hub (thub) + TUI
- distro/: camel.toml manifest + MANIFEST.md (Arch + [tanin] repo model)
- packaging/: taninux, tanin-desktop (niri metapackage), tanin-greet,
  tanin-libadwaita, tanin-setup
- docs/, data/, LICENSE (GPL-3.0-or-later)

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

packaging/tanin-greet/config.toml

@@ -0,0 +1,8 @@
+# greetd config for tanin-greet (TANINUX custom GTK4 greeter).
+# The greeter is a GTK app, so it's hosted by `cage` (one-window kiosk compositor).
+[terminal]
+vt = 1
+
+[default_session]
+command = "cage -s -- tanin-greet"
+user = "greeter"