[client/ui] Introduce localisation (i18n + preferences) feature packages

Adds a tray + React translation pipeline driven by a single JSON locale
tree (frontend/src/i18n/locales) embedded into the Go binary. The tray
re-renders on language switch via a Localizer that subscribes to the
preferences store.

Layout:
- client/ui/i18n: Bundle, LanguageCode, Language, errors, embedded-FS
  loader. Pure domain, no Wails/daemon deps.
- client/ui/preferences: Store + UIPreferences for user-scope UI state,
  persisted under os.UserConfigDir()/netbird/ui-preferences.json with
  atomic writes and a subscribe/broadcast channel.
- client/ui/services: thin Wails-binding facades (services.I18n,
  services.Preferences) so React sees ctx-first signatures.
- client/ui/localizer.go: tray bridge that owns the active language,
  exposes T()/StatusLabel() and re-paints the menu on prefs change.
- tray.go: every user-facing const replaced by translation keys via
  t.loc.T(...); menu rebuild + state replay on language switch.
- main.go: //go:embed all:frontend/src/i18n/locales, wires Bundle ->
  Store -> Localizer -> Wails facades in order.

Frontend API exposed via Wails bindings: I18n.Languages, I18n.Bundle,
Preferences.Get, Preferences.SetLanguage, plus the
netbird:preferences:changed event.

Includes regenerated Wails TS bindings (peers/profileswitcher/etc.
re-emitted as part of the build) and en/hu seed bundles.

client/ui/localizer.go

@@ -0,0 +1,133 @@
+//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 is the tray's bridge to the i18n bundle and preferences store.
+// It caches the active language so every menu-build pass and notification
+// call can resolve a key without re-querying preferences, and it owns
+// the preference-subscription lifecycle so consumers don't have to.
+//
+// Kept in the main package (not i18n/) because StatusLabel maps daemon
+// status enum strings (services.StatusIdle, services.StatusDaemonUnavailable)
+// to translations — pulling those into i18n 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 so
+// the first menu render is already in the right locale. Either argument
+// may be nil — useful for tests/dry-runs — in which case Translate falls
+// back to 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 BCP-47 code currently driving translations.
+func (l *Localizer) Language() i18n.LanguageCode {
+	l.mu.RLock()
+	defer l.mu.RUnlock()
+	return l.lang
+}
+
+// T resolves key in the current language with optional {placeholder}/value
+// argument pairs. When no bundle is wired the key is returned as-is so
+// callers always get a non-empty string.
+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 subscribes to preference changes; cb fires for each new language
+// (after the Localizer's own cached language has been updated, so cb can
+// call l.T to render with the new locale). Safe to call once per
+// Localizer; later calls overwrite the previous 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 drops the preference subscription. Currently unused (the tray
+// lives for the whole process) but kept so a future shutdown path can
+// release the channel cleanly.
+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 user-facing tray label.
+// Idle and the daemon-unavailable sentinel get translated phrasing; every
+// other status passes through verbatim (matches the legacy behaviour of
+// surfacing the raw daemon enum for the connecting/needs-login states).
+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")
+	}
+	return status
+}