feat: implement group management and parallel execution in manage.sh

manage.conf

@@ -0,0 +1,26 @@
+# Global maximum number of stacks executed concurrently within a group.
+# Use 0 for unlimited concurrency.
+max_parallel 2
+
+# Groups run from top to bottom for up/start/restart/pull/update.
+# They run from bottom to top for stop/down.
+group gateway --parallel 1 \
+	nginx
+
+group network \
+	adguardhome \
+	ddns-go
+
+group services \
+	samba \
+	immich \
+	gitea \
+	openlist \
+	homeassistant \
+	qbittorrent
+
+group backup --parallel 1 \
+	backrest
+
+# Excluded stacks are ignored by all bulk commands.
+# exclude experimental-stack