[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/internal/engine_session_deadline_test.go

@@ -0,0 +1,78 @@
+package internal
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/types/known/timestamppb"
+
+	"github.com/netbirdio/netbird/client/internal/auth/sessionwatch"
+	"github.com/netbirdio/netbird/client/internal/peer"
+)
+
+// TestApplySessionDeadline_ThreeState pins down the 3-state semantics of the
+// wire field carried on LoginResponse / SyncResponse:
+//
+//   - nil pointer            → no info; previously-anchored deadline survives
+//   - explicit zero value    → "expiry disabled" sentinel; both sinks cleared
+//   - valid future timestamp → new deadline propagated to both sinks
+func TestApplySessionDeadline_ThreeState(t *testing.T) {
+	newEngine := func() *Engine {
+		recorder := peer.NewRecorder("")
+		return &Engine{
+			statusRecorder: recorder,
+			sessionWatcher: sessionwatch.New(recorder),
+		}
+	}
+
+	t.Run("valid timestamp sets deadline on both sinks", func(t *testing.T) {
+		e := newEngine()
+		deadline := time.Now().Add(time.Hour).UTC().Truncate(time.Second)
+
+		e.ApplySessionDeadline(timestamppb.New(deadline))
+
+		require.True(t, e.statusRecorder.GetSessionExpiresAt().Equal(deadline),
+			"status recorder should hold the new deadline")
+	})
+
+	t.Run("nil is a no-op and preserves previous deadline", func(t *testing.T) {
+		e := newEngine()
+		seeded := time.Now().Add(time.Hour).UTC().Truncate(time.Second)
+		e.ApplySessionDeadline(timestamppb.New(seeded))
+		require.True(t, e.statusRecorder.GetSessionExpiresAt().Equal(seeded))
+
+		e.ApplySessionDeadline(nil)
+
+		require.True(t, e.statusRecorder.GetSessionExpiresAt().Equal(seeded),
+			"nil snapshot must not disturb the existing deadline")
+	})
+
+	t.Run("explicit zero clears a previously-anchored deadline", func(t *testing.T) {
+		e := newEngine()
+		seeded := time.Now().Add(time.Hour).UTC().Truncate(time.Second)
+		e.ApplySessionDeadline(timestamppb.New(seeded))
+		require.True(t, e.statusRecorder.GetSessionExpiresAt().Equal(seeded))
+
+		// Explicit zero Timestamp{} (seconds=0, nanos=0) is the
+		// "expiry disabled / not SSO" sentinel.
+		e.ApplySessionDeadline(&timestamppb.Timestamp{})
+
+		require.True(t, e.statusRecorder.GetSessionExpiresAt().IsZero(),
+			"explicit zero sentinel must clear the deadline")
+	})
+
+	t.Run("invalid timestamp clears the deadline", func(t *testing.T) {
+		e := newEngine()
+		seeded := time.Now().Add(time.Hour).UTC().Truncate(time.Second)
+		e.ApplySessionDeadline(timestamppb.New(seeded))
+		require.True(t, e.statusRecorder.GetSessionExpiresAt().Equal(seeded))
+
+		// Out-of-range nanos → IsValid()==false; same-meaning as the
+		// disabled sentinel for downstream sinks.
+		e.ApplySessionDeadline(&timestamppb.Timestamp{Seconds: 1, Nanos: -1})
+
+		require.True(t, e.statusRecorder.GetSessionExpiresAt().IsZero(),
+			"invalid timestamp must clear the deadline")
+	})
+}