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/desktop/ui/style.css

@@ -0,0 +1,101 @@
+* {
+  margin: 0;
+  box-sizing: border-box;
+}
+
+html,
+body {
+  height: 100%;
+}
+
+body {
+  display: grid;
+  place-items: center;
+  background: #0b0d11;
+  color: #e7e7ea;
+  font-family:
+    system-ui,
+    -apple-system,
+    "Segoe UI",
+    Roboto,
+    sans-serif;
+  -webkit-font-smoothing: antialiased;
+}
+
+.card {
+  width: min(24rem, calc(100vw - 3rem));
+  padding: 2.5rem 2rem;
+  background: #14161b;
+  border: 1px solid #26292f;
+  border-radius: 14px;
+  text-align: center;
+}
+
+.logo {
+  width: 56px;
+  height: 56px;
+  border-radius: 12px;
+  margin-bottom: 1rem;
+}
+
+h1 {
+  font-size: 1.4rem;
+  font-weight: 600;
+  letter-spacing: -0.01em;
+}
+
+.sub {
+  margin-top: 0.4rem;
+  color: #9a9aa3;
+  font-size: 0.9rem;
+}
+
+form {
+  display: flex;
+  flex-direction: column;
+  gap: 0.75rem;
+  margin-top: 1.75rem;
+}
+
+input {
+  padding: 0.65rem 0.8rem;
+  background: #0b0d11;
+  border: 1px solid #2e3239;
+  border-radius: 8px;
+  color: inherit;
+  font-size: 0.95rem;
+  outline: none;
+}
+
+input:focus {
+  border-color: #f4693a;
+}
+
+button {
+  padding: 0.65rem 0.8rem;
+  background: #f4693a;
+  border: none;
+  border-radius: 8px;
+  color: #fff;
+  font-size: 0.95rem;
+  font-weight: 600;
+  cursor: pointer;
+}
+
+button:disabled {
+  opacity: 0.6;
+  cursor: default;
+}
+
+.err {
+  margin-top: 0.9rem;
+  color: #ef6b6b;
+  font-size: 0.85rem;
+}
+
+.hint {
+  margin-top: 1.5rem;
+  color: #6d6d76;
+  font-size: 0.78rem;
+  line-height: 1.5;
+}