Fix admin authorization and harden chat requests

src/middleware/asyncHandler.js

@@ -0,0 +1,3 @@
+/** Forward rejected route promises to Express 4's error middleware. */
+export const asyncHandler = (handler) => (req, res, next) =>
+    Promise.resolve().then(() => handler(req, res, next)).catch(next);

src/middleware/auth.js

@@ -7,3 +7,10 @@ export function requireLogin(req, res, next) {
     }
     return next();
 }
+
+export function requireAdmin(req, res, next) {
+    if (req.account?.role !== "admin") {
+        return res.status(403).json({error: "Admin only"});
+    }
+    return next();
+}