fix(node): keep client/inbound edits working when a node is offline (#4923, #4931)

Node-backed client and inbound edits no longer hard-fail when the backing node is offline or disabled. Edits commit to the panel DB immediately and reconcile to the node when it reconnects (eventual consistency); the panel is the single source of truth for desired config.

- Add Node.ConfigDirty/ConfigDirtyAt; mark a node dirty when an edit commits without reaching it (cleared via CAS on ConfigDirtyAt after a full reconcile).
- nodePushPlan() reads node state fresh from the DB, skips the push for offline/disabled nodes (no 10s hang), and treats push failures as non-fatal across every mutation path (client add/update/del + bulk + attach/detach; inbound add/update/del/toggle/resetTraffic).
- ReconcileNode() pushes the panel's desired config to a node on reconnect (refreshing the remote tag cache first) and prunes node-side orphans; runs before the traffic pull in the node sync job.
- While a node is dirty the traffic pull applies only up/down deltas and node-initiated disables, never overwriting desired config from a stale node snapshot.
- Surface a non-blocking 'saved; will sync on reconnect' warning to the UI.

Validated with a two-panel Docker E2E: client delete/update, attach/detach, and inbound add/delete all reconcile correctly offline -> reconnect.

web/controller/util.go

@@ -182,6 +182,16 @@ func jsonMsgObj(c *gin.Context, msg string, obj any, err error) {
 	c.JSON(http.StatusOK, m)
 }
 
+// pendingNodeObj returns a response object flagging that the save committed
+// locally but a backing node was offline/disabled, so the change will be
+// mirrored to the node once it reconnects. Returns nil when nothing is pending.
+func pendingNodeObj(pending bool) any {
+	if pending {
+		return gin.H{"nodePending": true}
+	}
+	return nil
+}
+
 // pureJsonMsg sends a pure JSON message response with custom status code.
 func pureJsonMsg(c *gin.Context, statusCode int, success bool, msg string) {
 	c.JSON(statusCode, entity.Msg{