[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/README.md

@@ -0,0 +1,85 @@
+# NetBird desktop UI (Wails3 + React)
+
+Replaces `client/ui` (Fyne). One binary on Windows / macOS / Linux,
+talks to the NetBird daemon over gRPC, renders a React frontend in a
+WebView.
+
+## Prerequisites
+
+- Go ≥ 1.25, Node ≥ 20, **pnpm** (`corepack enable && corepack prepare pnpm@latest --activate`)
+- `wails3` CLI: `go install github.com/wailsapp/wails/v3/cmd/wails3@latest`
+- `task`: `go install github.com/go-task/task/v3/cmd/task@latest`
+- A running NetBird daemon (default: `unix:///var/run/netbird.sock`,
+  Windows `tcp://127.0.0.1:41731`)
+- Linux only: `libwebkit2gtk-4.1-dev`, `libgtk-3-dev`,
+  `libayatana-appindicator3-dev`
+
+## Develop without rebuilding
+
+```bash
+cd client/ui-wails
+task dev
+```
+
+`task dev` runs Vite (port 9245) + the Go binary + a `*.go` watcher.
+Frontend edits hot-reload instantly. Go edits trigger a rebuild and
+relaunch. Pass daemon flags after `--`:
+
+```bash
+task dev -- --daemon-addr=tcp://127.0.0.1:41731
+```
+
+For pure UI work (no native window, fastest loop):
+
+```bash
+cd frontend && pnpm dev
+```
+
+## Production build
+
+```bash
+task build
+```
+
+Output in `bin/`. Frontend assets are embedded into the binary.
+
+### Cross-compile Windows from Linux
+
+Install the mingw-w64 toolchain once:
+
+```bash
+sudo apt install gcc-mingw-w64-x86-64           # Debian/Ubuntu
+sudo dnf install mingw64-gcc                    # Fedora
+sudo pacman -S mingw-w64-gcc                    # Arch
+```
+
+Then:
+
+```bash
+CGO_ENABLED=1 task windows:build
+```
+
+Produces `bin/netbird-ui.exe`. macOS cross-compile from Linux is not
+supported (signing and notarization need a real Mac).
+
+## Regenerating bindings
+
+When a Go service signature changes:
+
+```bash
+wails3 generate bindings
+```
+
+`task dev` does this automatically on `*.go` save.
+
+## Tray icons
+
+Source SVGs live in `assets/svg/` (state.svg + state-macos.svg). After editing
+any SVG, rasterize to the PNGs the Go side embeds:
+
+```bash
+task common:generate:tray:icons
+```
+
+Requires Inkscape. Commit the resulting `assets/*.png` files alongside the
+SVG change so CI doesn't need Inkscape installed.