P7: restore agent node type, agent heartbeat expiry, build-version injection, remove log/history/xray-metrics modules, optional sub port

- nodes: port node-type (traditional/agent) picker back from web-src into
  the embedded frontend; backend annotates NodeView.nodeType from
  agent_nodes bindings; fix agent-node update path (skip reachability
  probe and apiToken requirement for agent-managed nodes); restore i18n
  keys in all 13 locales; install command now uses the Gitea mirror
- jobs: expire agent-bound nodes whose agent_nodes.last_seen is older
  than max(3x heartbeat interval, 120s) = 180s; last_seen=0 (never
  registered) is left untouched; transitions reuse UpdateHeartbeat +
  node event broadcast
- config: GetBaseVersion honors ldflags-injected buildVersion; release
  builds inject 3.7.0-agent.1 so the panel no longer reports a phantom
  update against the Gitea release tag
- logger/server: remove the three log viewers (panel/xray/amneziawg),
  their API endpoints and the 10240-entry in-memory log buffer; file
  logging via lumberjack unchanged; tests assert via a new optional
  logger hook instead of the removed buffer
- server: remove system history and xray metrics modules end to end
  (endpoints, sampling appends in RefreshStatus, per-minute persist
  cron, gob snapshot/restore, XrayMetricsService); realtime status and
  per-node history are untouched
- settings: subPort may be 0/unset - subscription links are generated
  without a port while the subscription service keeps binding the
  default 2096; the settings form declares the cleared state via
  onNumber's new onClear option instead of snapping back to 1

internal/web/controller/node.go

@@ -169,6 +169,7 @@ func (a *NodeController) add(c *gin.Context) {
 	// For agent nodes, issue an agent token bound to the new node and
 	// return it so the UI can display it (shown only once).
 	if isAgent {
+		view.NodeType = "agent"
 		nodeID := view.Id
 		token, _, err := issueAgentToken(&nodeID, n.Name)
 		if err != nil {
@@ -200,7 +201,10 @@ func (a *NodeController) update(c *gin.Context) {
 		jsonMsg(c, I18nWeb(c, "pages.nodes.toasts.obtain"), err)
 		return
 	}
-	if n.OutboundTag == "" && old.OutboundTag == "" && (!n.ClearApiToken || n.Enable) {
+	// Agent nodes have no panel to probe and no panel API token; editing one
+	// must skip the reachability check exactly like creation does.
+	isAgent := n.NodeType == "agent" || a.nodeService.IsAgentManaged(id)
+	if !isAgent && n.OutboundTag == "" && old.OutboundTag == "" && (!n.ClearApiToken || n.Enable) {
 		if err := a.ensureReachable(c, n, id); err != nil {
 			jsonMsg(c, I18nWeb(c, "pages.nodes.toasts.update"), err)
 			return