feat(auth): two-role permission system (admin/member)

Adds an admin/member role to WebUI auth. /api/users and /api/audit
are now gated by a requireAdmin middleware; all other authenticated
endpoints accept both roles. Schema migration defaults all existing
users to admin to preserve access. POST /api/users defaults new users
to member; first-run setup always creates an admin. Adds PATCH
/api/users/:id/role with last-admin demotion and deletion guards.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/web/middleware/requireAdmin.test.ts

@@ -0,0 +1,50 @@
+import { describe, it, expect, beforeEach, afterEach } from "vitest";
+import express from "express";
+import cookieParser from "cookie-parser";
+import request from "supertest";
+import { createDatabase, type BotDatabase } from "../../data/database.js";
+import { createUserStore } from "../../data/users.js";
+import { createSessionStore } from "../../data/sessions.js";
+import { createRequireAuth } from "./requireAuth.js";
+import { requireAdmin } from "./requireAdmin.js";
+import { SESSION_COOKIE_NAME } from "../auth/validateSession.js";
+
+describe("requireAdmin middleware", () => {
+  let botDb: BotDatabase;
+  let app: express.Express;
+  let adminCookie: string;
+  let memberCookie: string;
+
+  beforeEach(async () => {
+    botDb = createDatabase(":memory:");
+    const users = createUserStore(botDb.db);
+    const sessions = createSessionStore(botDb.db);
+    const admin = await users.createUser("admin", "pw-admin-pw", "admin");
+    const member = await users.createUser("member", "pw-member-pw", "member");
+    adminCookie = `${SESSION_COOKIE_NAME}=${sessions.createSession(admin.id).token}`;
+    memberCookie = `${SESSION_COOKIE_NAME}=${sessions.createSession(member.id).token}`;
+    app = express();
+    app.use(cookieParser());
+    app.use(createRequireAuth(sessions));
+    app.use(requireAdmin);
+    app.get("/admin-only", (_req, res) => res.json({ ok: true }));
+  });
+
+  afterEach(() => botDb.close());
+
+  it("rejects unauthenticated requests with 401", async () => {
+    const res = await request(app).get("/admin-only");
+    expect(res.status).toBe(401);
+  });
+
+  it("rejects member with 403", async () => {
+    const res = await request(app).get("/admin-only").set("Cookie", memberCookie);
+    expect(res.status).toBe(403);
+    expect(res.body).toEqual({ error: "forbidden" });
+  });
+
+  it("allows admin", async () => {
+    const res = await request(app).get("/admin-only").set("Cookie", adminCookie);
+    expect(res.status).toBe(200);
+  });
+});