Fix paru PKGBUILD repo name collision with pacman registry

Both the pacman package registry and the paru PKGBUILD repo used
[moonarch] as section name, causing paru to fail resolving PKGBUILD
upgrade targets against the wrong repo. Renamed PKGBUILD repo to
[moonarch-pkgbuilds] and moved config from ~/.config/paru/paru.conf
to system-wide /etc/paru.conf.

scripts/post-install.sh

@@ -51,13 +51,16 @@ rm -f "$KEY_FILE"
 # --- Set up Moonarch custom paru repo ---
 
 log "Setting up Moonarch paru repo..."
-PARU_CONF="$HOME/.config/paru/paru.conf"
-mkdir -p "$(dirname "$PARU_CONF")"
-if ! grep -q '\[moonarch\]' "$PARU_CONF" 2>/dev/null; then
-    cat >> "$PARU_CONF" <<'EOCONF'
-[moonarch]
-Url = https://gitea.moonarch.de/nevaforget/moonarch-pkgbuilds.git
-EOCONF
+PARU_CONF="/etc/paru.conf"
+if ! grep -q 'Mode.*p' "$PARU_CONF" 2>/dev/null; then
+    sudo sed -i '/^\[options\]/a Mode = arp' "$PARU_CONF"
+    log "  + Mode = arp set in paru.conf."
+else
+    log "  ~ Mode already includes pkgbuilds."
+fi
+if ! grep -q '\[moonarch-pkgbuilds\]' "$PARU_CONF" 2>/dev/null; then
+    printf '\n[moonarch-pkgbuilds]\nUrl = https://gitea.moonarch.de/nevaforget/moonarch-pkgbuilds.git\n' \
+        | sudo tee -a "$PARU_CONF" > /dev/null
     log "  + Moonarch repo added to paru.conf."
 else
     log "  ~ Moonarch repo already in paru.conf."