security: default-deny /api middleware allowlist (#44)

Previously middleware.ts listed /api/ as a public prefix, so any new
API route added under /api/** was served without a session check
unless the developer remembered to self-authenticate it. The
middleware now returns 404 for any /api path not explicitly
allowlisted (auth, trpc, sse, cron, reports, health, ready, perf) —
adding a new API route is a deliberate allowlist edit. verifyCronSecret
was already fail-closed when CRON_SECRET is unset; added unit tests.

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

apps/web/src/middleware.test.ts

@@ -4,9 +4,8 @@ import { NextRequest } from "next/server";
 // Simulate an authenticated session so the middleware does not redirect
 // and CSP headers are set on every response.
 vi.mock("./server/auth-edge.js", () => ({
-  auth: (handler: (req: NextRequest & { auth: object | null }) => unknown) =>
-    (req: NextRequest) =>
-      handler(Object.assign(req, { auth: { user: { id: "test-user", email: "test@test.com" } } })),
+  auth: (handler: (req: NextRequest & { auth: object | null }) => unknown) => (req: NextRequest) =>
+    handler(Object.assign(req, { auth: { user: { id: "test-user", email: "test@test.com" } } })),
 }));
 
 async function importMiddleware(nodeEnv: string) {
@@ -82,3 +81,49 @@ describe("middleware — Content-Security-Policy", () => {
     }
   });
 });
+
+describe("middleware — API allowlist (default-deny)", () => {
+  afterEach(() => {
+    vi.unstubAllEnvs();
+    vi.resetModules();
+  });
+
+  it("allows allowlisted API routes through", async () => {
+    const middleware = await importMiddleware("production");
+    for (const url of [
+      "http://localhost:3100/api/trpc/project.list",
+      "http://localhost:3100/api/auth/signin",
+      "http://localhost:3100/api/sse/timeline",
+      "http://localhost:3100/api/cron/health-check",
+      "http://localhost:3100/api/reports/allocations",
+      "http://localhost:3100/api/health",
+      "http://localhost:3100/api/ready",
+      "http://localhost:3100/api/perf",
+    ]) {
+      const res = await middleware(new NextRequest(url));
+      expect(res.status).not.toBe(404);
+    }
+  });
+
+  it("returns 404 for non-allowlisted /api/* routes", async () => {
+    const middleware = await importMiddleware("production");
+    for (const url of [
+      "http://localhost:3100/api/debug",
+      "http://localhost:3100/api/internal/secret",
+      "http://localhost:3100/api/admin/users",
+    ]) {
+      const res = await middleware(new NextRequest(url));
+      expect(res.status).toBe(404);
+    }
+  });
+});
+
+describe("isApiAllowlisted helper", () => {
+  it("exported via module for testing", async () => {
+    const { isApiAllowlisted } = await import("./middleware.js");
+    expect(isApiAllowlisted("/api/trpc/foo")).toBe(true);
+    expect(isApiAllowlisted("/api/debug")).toBe(false);
+    expect(isApiAllowlisted("/api/healthz")).toBe(false);
+    expect(isApiAllowlisted("/api/health")).toBe(true);
+  });
+});