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-setup/tanin-session.target

@@ -0,0 +1,7 @@
+[Unit]
+Description=TANINUX graphical session
+# Startet (per Dependency-Request) graphical-session.target, an dem
+# xdg-desktop-portal hängt — sonst kann das Portal nicht aktivieren und
+# libadwaita-Apps (Nautilus …) bleiben im Hell-Fallback.
+Requires=graphical-session.target
+After=graphical-session.target