[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/ui/localizer.go

@@ -0,0 +1,130 @@
+//go:build !android && !ios && !freebsd && !js
+
+package main
+
+import (
+	"strings"
+	"sync"
+
+	log "github.com/sirupsen/logrus"
+
+	"github.com/netbirdio/netbird/client/ui/i18n"
+	"github.com/netbirdio/netbird/client/ui/preferences"
+	"github.com/netbirdio/netbird/client/ui/services"
+)
+
+// Localizer caches the active language so key lookups skip the preferences store.
+//
+// Kept in the main package (not i18n/) because StatusLabel maps daemon
+// status enum strings to translations; moving it would invert the
+// dependency direction.
+type Localizer struct {
+	bundle *i18n.Bundle
+	store  *preferences.Store
+
+	mu   sync.RWMutex
+	lang i18n.LanguageCode
+
+	unsubscribe func()
+}
+
+// NewLocalizer seeds the active language from the on-disk preference. Either
+// argument may be nil (tests): T then returns the raw key and Watch is a no-op.
+func NewLocalizer(bundle *i18n.Bundle, store *preferences.Store) *Localizer {
+	l := &Localizer{
+		bundle: bundle,
+		store:  store,
+		lang:   i18n.DefaultLanguage,
+	}
+	if store != nil {
+		if p := store.Get(); p.Language != "" {
+			l.lang = p.Language
+		}
+	}
+	return l
+}
+
+// Language returns the active language code.
+func (l *Localizer) Language() i18n.LanguageCode {
+	l.mu.RLock()
+	defer l.mu.RUnlock()
+	return l.lang
+}
+
+// T resolves key in the current language; args are {placeholder}/value pairs.
+// With no bundle wired it returns key unchanged.
+func (l *Localizer) T(key string, args ...string) string {
+	if l == nil || l.bundle == nil {
+		return key
+	}
+	l.mu.RLock()
+	lang := l.lang
+	l.mu.RUnlock()
+	return l.bundle.Translate(lang, key, args...)
+}
+
+// Watch invokes cb on each language change, after the cached language is
+// updated so cb may call l.T with the new locale. Replaces any prior subscription.
+func (l *Localizer) Watch(cb func(lang i18n.LanguageCode)) {
+	if l.store == nil {
+		return
+	}
+	ch, unsubscribe := l.store.Subscribe()
+	l.mu.Lock()
+	if l.unsubscribe != nil {
+		l.unsubscribe()
+	}
+	l.unsubscribe = unsubscribe
+	l.mu.Unlock()
+
+	go func() {
+		for p := range ch {
+			if p.Language == "" {
+				continue
+			}
+			l.mu.Lock()
+			if l.lang == p.Language {
+				l.mu.Unlock()
+				continue
+			}
+			l.lang = p.Language
+			l.mu.Unlock()
+			log.Infof("localizer: language switched to %s", p.Language)
+			if cb != nil {
+				cb(p.Language)
+			}
+		}
+	}()
+}
+
+// Close cancels the preference subscription.
+func (l *Localizer) Close() {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	if l.unsubscribe != nil {
+		l.unsubscribe()
+		l.unsubscribe = nil
+	}
+}
+
+// StatusLabel maps a daemon status string to its tray label; unrecognised
+// statuses pass through verbatim.
+func (l *Localizer) StatusLabel(status string) string {
+	switch {
+	case status == "", strings.EqualFold(status, services.StatusIdle):
+		return l.T("tray.status.disconnected")
+	case strings.EqualFold(status, services.StatusDaemonUnavailable):
+		return l.T("tray.status.daemonUnavailable")
+	case strings.EqualFold(status, services.StatusConnected):
+		return l.T("tray.status.connected")
+	case strings.EqualFold(status, services.StatusConnecting):
+		return l.T("tray.status.connecting")
+	case strings.EqualFold(status, services.StatusNeedsLogin):
+		return l.T("tray.status.needsLogin")
+	case strings.EqualFold(status, services.StatusLoginFailed):
+		return l.T("tray.status.loginFailed")
+	case strings.EqualFold(status, services.StatusSessionExpired):
+		return l.T("tray.status.sessionExpired")
+	}
+	return status
+}