[client] Add Wails3 + React desktop UI scaffold

Stage 1 of the client/ui (Fyne) replacement. Adds a new client/ui-wails
module that runs on Linux/macOS/Windows from a single React + Vite +
Tailwind frontend driven by a thin gRPC services layer in Go.

- Single-module integration (no submodule): merge Wails3 into root go.mod
  with build tags !android !ios !freebsd !js so cross-compiles on those
  targets exclude the package automatically.
- Seven gRPC-bound services: Connection, Settings, Networks, Profiles,
  Debug, Update, Peers. Peers bridges Status polling and SubscribeEvents
  to the Wails event bus (netbird:status, netbird:event).
- Tray + window shell mirrors the Fyne menu 1:1 with hide-on-close,
  SIGUSR1 / Windows named-event for external "show window" triggers.
- React pages cover functional parity for Status, Settings (3 tabs),
  Networks (3 tabs), Profiles, Debug, Update, QuickActions, LoginUrl.
- SVG-sourced tray icons (12 source SVGs incl. macOS template variants)
  rasterized to PNG via task common:generate:tray:icons.
- Linux launcher sets WEBKIT_DISABLE_DMABUF_RENDERER=1 in the .desktop
  Exec= line and in task linux:run so the app renders correctly under
  RDP, VirtualBox, KVM, and bare WMs (Fluxbox/dwm) without DRM access.

client/ui-wails/frontend/src/components/Tabs.tsx

@@ -0,0 +1,40 @@
+import { ReactNode, useState } from "react";
+import { cn } from "../lib/cn";
+
+interface Tab {
+  value: string;
+  label: string;
+  content: ReactNode;
+}
+
+interface Props {
+  tabs: Tab[];
+  initial?: string;
+}
+
+export function Tabs({ tabs, initial }: Props) {
+  const [active, setActive] = useState(initial ?? tabs[0]?.value);
+  return (
+    <div className="flex h-full flex-col">
+      <div className="flex shrink-0 gap-1 border-b border-nb-gray-200 dark:border-nb-gray-800">
+        {tabs.map((t) => (
+          <button
+            key={t.value}
+            onClick={() => setActive(t.value)}
+            className={cn(
+              "border-b-2 px-3 py-2 text-sm font-medium transition-colors",
+              active === t.value
+                ? "border-netbird text-netbird"
+                : "border-transparent text-nb-gray-500 hover:text-nb-gray-800 dark:hover:text-nb-gray-200",
+            )}
+          >
+            {t.label}
+          </button>
+        ))}
+      </div>
+      <div className="flex-1 overflow-auto">
+        {tabs.find((t) => t.value === active)?.content}
+      </div>
+    </div>
+  );
+}