[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/frontend/src/globals.css

@@ -0,0 +1,45 @@
+@font-face {
+    font-family: "Inter Variable";
+    font-style: normal;
+    font-weight: 100 900;
+    src: url("./assets/fonts/inter-variable.ttf") format("truetype");
+}
+
+@font-face {
+    font-family: "JetBrains Mono Variable";
+    font-style: normal;
+    font-weight: 100 800;
+    src: url("./assets/fonts/jetbrains-mono-variable.ttf") format("truetype");
+}
+
+@tailwind base;
+@tailwind components;
+@tailwind utilities;
+
+html,
+body,
+#root {
+    height: 100%;
+    overflow: hidden;
+}
+
+/*
+ * Body bg is fully opaque on purpose. The main window uses
+ * MacBackdropTranslucent (main.go) and TitleBarHiddenInset, which on macOS
+ * lets the desktop wallpaper bleed through any non-opaque pixel. A 90%
+ * body alpha meant two machines with different wallpapers saw different
+ * effective backgrounds. Matching Wails' BackgroundColour (#181A1D / nb-gray
+ * DEFAULT) here keeps things consistent regardless of the OS backdrop.
+ */
+body {
+    @apply bg-nb-gray font-sans text-nb-gray-200 antialiased;
+}
+
+.wails-draggable {
+    --wails-draggable: drag;
+    cursor: default;
+}
+
+.wails-no-draggable {
+    --wails-draggable: no-drag;
+}