[management,client] 0.75.0 release with new desktop UI (#6473)

- **Wails v3 application** (`client/ui`) with a React + TypeScript + Tailwind frontend replacing the Fyne UI: main connection view, exit-node switcher, networks/peers browser with detail panels, profile management, settings (general, network, SSH, security, troubleshooting, appearance), debug-bundle creation, and a first-run welcome flow.
- **Internationalization**: go-i18n bundle with 9 locales (en, de, es, fr, hu, it, pt, ru, zh-CN) shared between the tray and the frontend.
- **New system tray** implementation with per-platform theme-aware icons, including a native XEmbed host for Linux (`xembed_tray_linux.c`) and a Linux theme watcher.
- **Session handling**: auth session watcher (`client/internal/auth/sessionwatch`), pending login flow, session-expiration dialog and tray notifications, and `netbird login` improvements.
- **Daemon API extensions** (`daemon.proto`): status stream subscription, event stream, networks/exit-node selection endpoints, and richer full status — with probe throttling on the daemon side to protect against UI-driven request storms.
- **UI preferences store** persisted per profile, autostart management via the daemon (single source of truth in HKCU on Windows).
- **Build system**: Taskfile-based builds per platform (macOS, Linux, Windows), Docker cross-compilation images, MSIX/NSIS/nfpm/AppImage packaging, and a new `frontend-ui` CI workflow.

Co-authored-by: Zoltan Papp <zoltan.pmail@gmail.com>
Co-authored-by: Eduard Gert <kontakt@eduardgert.de>
Co-authored-by: braginini <bangvalo@gmail.com>
Co-authored-by: Pascal Fischer <32096965+pascal-fischer@users.noreply.github.com>
Co-authored-by: riccardom <riccardomanfrin@gmail.com>

client/server/mdm.go

@@ -100,7 +100,10 @@ func (s *Server) onMDMPolicyChange(_, _ *mdm.Policy) error {
 		proto.SystemEvent_SYSTEM,
 		"MDM policy applied",
 		"NetBird configuration was updated by your IT policy.",
-		map[string]string{"source": "mdm", "type": "policy_applied"},
+		map[string]string{
+			proto.MetadataSourceKey: proto.MetadataSourceMDM,
+			proto.MetadataTypeKey:   proto.MetadataTypePolicyApplied,
+		},
 	)
 	return nil
 }
@@ -125,8 +128,8 @@ func (s *Server) publishConfigChangedEvent(source string) {
 		fmt.Sprintf("daemon config changed (source=%s)", source),
 		"",
 		map[string]string{
-			"source": source,
-			"type":   "config_changed",
+			proto.MetadataSourceKey: source,
+			proto.MetadataTypeKey:   proto.MetadataTypeConfigChanged,
 		},
 	)
 }
@@ -161,7 +164,7 @@ func (s *Server) restartEngineForMDMLocked() error {
 	s.clientGiveUpChan = make(chan struct{})
 	log.Info("MDM restart: spawning connectWithRetryRuns with re-resolved config")
 	go s.connectWithRetryRuns(ctx, config, s.statusRecorder, s.clientRunningChan, s.clientGiveUpChan)
-	s.publishConfigChangedEvent("mdm")
+	s.publishConfigChangedEvent(proto.MetadataSourceMDM)
 	return nil
 }