security: tighten CSP — drop provider wildcards, add object/frame/worker-src (#45)

Browser code never calls OpenAI/Azure/Gemini directly; all AI traffic is
server-side tRPC. connect-src is now locked to 'self'. Added object-src 'none',
frame-src 'none', media-src 'self', and worker-src 'self' blob:. style-src
keeps 'unsafe-inline' for React + @react-pdf/renderer (documented residual
risk — script-src is nonce-based so CSS injection cannot escalate to JS).

Added three regression tests covering connect-src no-wildcards, object/frame-src
'none', and worker-src scope.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

apps/web/src/middleware.ts

@@ -32,6 +32,10 @@ function isPublicUiPath(pathname: string): boolean {
   return PUBLIC_UI_PREFIXES.some((prefix) => pathname.startsWith(prefix));
 }
 
+// Browser-side code never talks to AI providers directly — every OpenAI /
+// Azure / Gemini call goes through a server tRPC route. Therefore connect-src
+// is locked to 'self' with no wildcards (ticket #45). If a future feature
+// needs a browser-originated cross-origin request, add it explicitly here.
 function buildCsp(nonce: string, isProd: boolean): string {
   const scriptSrc = isProd ? `'self' 'nonce-${nonce}'` : `'self' 'unsafe-eval' 'unsafe-inline'`;
 
@@ -40,11 +44,19 @@ function buildCsp(nonce: string, isProd: boolean): string {
   return [
     "default-src 'self'",
     `script-src ${scriptSrc}`,
+    // style-src keeps 'unsafe-inline' because React inlines styles from
+    // component-scoped CSS and @react-pdf/renderer emits inline style blocks.
+    // A nonce-based style-src-elem breaks both. This is an accepted residual
+    // risk documented in docs/security-architecture.md §5.
     "style-src 'self' 'unsafe-inline'",
     `img-src ${imgSrc}`,
     "font-src 'self' data:",
-    "connect-src 'self' https://generativelanguage.googleapis.com https://*.openai.com https://*.azure.com",
+    "connect-src 'self'",
     "frame-ancestors 'none'",
+    "frame-src 'none'",
+    "object-src 'none'",
+    "media-src 'self'",
+    "worker-src 'self' blob:",
     "base-uri 'self'",
     "form-action 'self'",
   ].join("; ");