Add missing packages for SonicDE: KDE Gear 26.04.3, KF6 6.29.0, and support packages.

Also adds manually built Plasma 6.7.4 packages (plasma-systemsettings,
plasma-keyboard/kcm, plasma-print-manager, flatpak-kcm, sddm, sddm-kcm,
kdebugsettings) and provides plasma-desktop-doc from sonic-desktop-interface-doc.

Build-order regenerated.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

sddm/sddm-greeter.pam

@@ -0,0 +1,17 @@
+#%PAM-1.0
+
+# Load environment from /etc/environment and ~/.pam_environment
+auth		required pam_env.so
+
+# Always let the greeter start without authentication
+auth		required pam_permit.so
+
+# No action required for account management
+account		required pam_permit.so
+
+# Can't change password
+password	required pam_deny.so
+
+# Setup session
+session		required pam_unix.so
+session		optional pam_systemd.so