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]>

.gitignore

@@ -18,8 +18,14 @@ bin
 
 # Build artifacts
 apps/frontend/dist
+apps/frontend/dev-dist
 apps/auth/dist
 packages/api-client/generated
+dist-release
+
+# Rust / Tauri
+apps/desktop/src-tauri/target
+apps/desktop/src-tauri/gen/schemas
 
 # Runtime data
 infra/data