chore(security): harden public surface (2026-09-06)

SECURITY.md

@@ -1,6 +1,6 @@
 # Security Assessment — CollabSpace
 
-**Date:** 2026-08-21  
+**Date:** 2026-09-06  
 **Scope:** Auth, XSS, injection, RLS, secrets, CORS, dependency risk  
 **Context:** Public Vercel deploy is a **frontend-only shell** (no Supabase env). Full multiplayer needs a Supabase project. Schema in `supabase/migrations/0001_init.sql` is **open RLS** (no auth).
 
@@ -147,3 +147,11 @@ npm run typecheck
 npm run test:e2e
 npm audit --omit=dev
 ```
+
+## Repository visibility
+
+This repository is currently **public** for portfolio review. When the open-source
+build story is no longer needed, **the GitHub repo will go private**. Making the
+repo private reduces source disclosure; it does **not** replace strong production
+secrets, auth allow-lists, webhook signatures, or Vercel/Actions environment
+hygiene. Rotate any credential that was pasted into chat, tickets, or screenshots.

vercel.json

@@ -4,6 +4,44 @@
   "outputDirectory": "client/dist",
   "framework": null,
   "rewrites": [
-    { "source": "/(.*)", "destination": "/index.html" }
+    {
+      "source": "/(.*)",
+      "destination": "/index.html"
+    }
+  ],
+  "headers": [
+    {
+      "source": "/(.*)",
+      "headers": [
+        {
+          "key": "X-Frame-Options",
+          "value": "DENY"
+        },
+        {
+          "key": "X-Content-Type-Options",
+          "value": "nosniff"
+        },
+        {
+          "key": "Referrer-Policy",
+          "value": "strict-origin-when-cross-origin"
+        },
+        {
+          "key": "Permissions-Policy",
+          "value": "camera=(), microphone=(), geolocation=(), payment=(), usb=()"
+        },
+        {
+          "key": "Strict-Transport-Security",
+          "value": "max-age=63072000; includeSubDomains; preload"
+        },
+        {
+          "key": "Cross-Origin-Opener-Policy",
+          "value": "same-origin"
+        },
+        {
+          "key": "X-DNS-Prefetch-Control",
+          "value": "off"
+        }
+      ]
+    }
   ]
 }