feat(nodes): bulk panel self-update with live online indicator

Adds the ability to update node panels to the latest release from the Nodes
page: select online, enabled nodes (checkboxes) and trigger their official
self-updater, or use the per-row Update action. A node whose reported panel
version trails the latest GitHub release is flagged with an 'update available'
tag (compared via lib/panel-version, mirroring the Go isNewerVersion).

Backend: Remote.UpdatePanel calls the node's existing
POST /panel/api/server/updatePanel; NodeService.UpdatePanels fans out over the
selected ids, skipping disabled/offline nodes with a per-node reason; exposed
as POST /panel/api/nodes/updatePanel (documented in endpoints.ts + openapi.json).

The bulk request sends a JSON body, so it sets Content-Type: application/json
explicitly — axios defaults POST to form-urlencoded, which made ShouldBindJSON
fail with 'invalid character i'.

Also reuses the clients-page online cue on the Nodes page: a pulsing green dot
plus green label for an online node. The .online-dot style moved to the shared
styles/utils.css so both pages load it.

Translations for all new node keys added across every language file.

web/runtime/remote.go

@@ -320,6 +320,14 @@ func (r *Remote) RestartXray(ctx context.Context) error {
 	return err
 }
 
+// UpdatePanel asks the node to run its own official self-updater (update.sh)
+// and restart onto the latest release. The node returns as soon as the job is
+// launched; the new version surfaces on the next heartbeat.
+func (r *Remote) UpdatePanel(ctx context.Context) error {
+	_, err := r.do(ctx, http.MethodPost, "panel/api/server/updatePanel", nil)
+	return err
+}
+
 func (r *Remote) ResetClientTraffic(ctx context.Context, _ *model.Inbound, email string) error {
 	_, err := r.do(ctx, http.MethodPost,
 		"panel/api/clients/resetTraffic/"+url.PathEscape(email), nil)