feat(desktop,server,web): app icons, completion notifications, single-user mode, bundled penguin CLI (#226)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

packages/server/src/http/routes/desktop.ts

@@ -1,15 +1,37 @@
 /**
- * Desktop-mode routes: POST /api/desktop/shutdown.
+ * Desktop-mode routes: POST /api/desktop/shutdown, plus the shared desktop-mode guard
+ * that turns off multi-user surfaces (see rejectInDesktopMode).
  *
- * Authenticated by the shell's Bearer token, not the cookie session (the shell holds no
- * cookie), so this mounts OUTSIDE authMiddleware and only when desktop mode is enabled.
- * Responds 202 first, then triggers the graceful shutdown a beat later so the response
- * isn't cut off by the closing listener.
+ * The shutdown route is authenticated by the shell's Bearer token, not the cookie
+ * session (the shell holds no cookie), so it mounts OUTSIDE authMiddleware and only
+ * when desktop mode is enabled. Responds 202 first, then triggers the graceful
+ * shutdown a beat later so the response isn't cut off by the closing listener.
  */
 import { Hono } from "hono";
+import type { MiddlewareHandler } from "hono";
 import { HttpError } from "../errors.js";
 import type { AppDeps } from "../../app.js";
 
+/**
+ * Guard for user-management surfaces (admin users, Project members): the desktop app is
+ * single-user, so the whole surface answers 403 with a dedicated code rather than being
+ * unmounted — a stray client gets a clear, localizable error instead of a 404. Existing
+ * users and memberships in the data root are untouched; only the management routes are
+ * closed while the server runs under the desktop shell.
+ */
+export function rejectInDesktopMode(deps: AppDeps): MiddlewareHandler {
+  return async (_c, next) => {
+    if (deps.desktop !== null) {
+      throw new HttpError(
+        403,
+        "desktop_single_user",
+        "User management is disabled in the desktop app (single-user mode).",
+      );
+    }
+    await next();
+  };
+}
+
 /** Delay between answering 202 and starting shutdown: lets the response flush. */
 const SHUTDOWN_DELAY_MS = 50;