feat(install): drop paru --pkgbuilds fallback, registry is the only path

The moonarch.install hook used to ensure /etc/paru.conf had Mode = arp
and a [moonarch-pkgbuilds] section. Both exist to let paru resolve
moonarch packages from a PKGBUILD repo — a second mechanism parallel
to the Arch registry, redundant now that the registry DB is stable.

Hook now strips the legacy config on next upgrade. Bump pkgrel so every
installed system picks up the cleanup.

moonarch-git/moonarch.install

@@ -42,16 +42,13 @@ post_install() {
         fi
     done < /etc/passwd
 
-    # Ensure paru PKGBUILD repo is configured (breaks bootstrap loop otherwise)
+    # Clean up legacy paru PKGBUILD-repo config. Moonarch now ships binaries
+    # exclusively through the Arch registry (pacman repo in /etc/pacman.conf);
+    # the [moonarch-pkgbuilds] section and Mode = arp are obsolete.
     PARU_CONF="/etc/paru.conf"
     if [ -f "$PARU_CONF" ]; then
-        if ! grep -q 'Mode.*p' "$PARU_CONF" 2>/dev/null; then
-            sed -i '/^\[options\]/a Mode = arp' "$PARU_CONF"
-        fi
-        if ! grep -q '\[moonarch-pkgbuilds\]' "$PARU_CONF" 2>/dev/null; then
-            printf '\n[moonarch-pkgbuilds]\nUrl = https://gitea.moonarch.de/nevaforget/moonarch-pkgbuilds.git\n' \
-                >> "$PARU_CONF"
-        fi
+        sed -i '/^Mode[[:space:]]*=[[:space:]]*arp\s*$/d' "$PARU_CONF"
+        sed -i '/^\[moonarch-pkgbuilds\]$/,/^$/d' "$PARU_CONF"
     fi
 
     # Cleanup legacy user-level configs (moved to system-level)