feat: phase 5 distribution — tauri shell, pwa, desktop release artifacts

- apps/desktop: Tauri 2 thin shell; connect screen stores the deployment
  URL, webview renders the remote console, tray with Show/Change Server/
  Quit, close-to-tray, single-instance
- frontend: vite-plugin-pwa generates manifest + Workbox SW (shell
  precache, /api /auth /mailpit NetworkOnly), install banner on
  beforeinstallprompt, rasterized PWA icons
- release.yml: desktop bundle matrix (linux/macos/windows) attached to
  GitHub Releases
- workspace 0.5.0; Dockerfiles copy the desktop workspace manifest

Authored By: TDvorak <[email protected]>

apps/frontend/src/App.tsx

@@ -31,6 +31,7 @@ import {
   NetworkError,
   OnboardingModal,
   ProjectDashboard,
+  PwaInstallBanner,
   type PaletteCommand,
   type ViewType,
 } from "./components";
@@ -1500,6 +1501,7 @@ export default function App() {
         <Show when={platformMessage()}>
           <div class="message message-neutral mb-5">{platformMessage()}</div>
         </Show>
+        <PwaInstallBanner />
 
         <Show
           when={platform() || isDemo}