feat(auth): user-management audit log (table + record sites + /api/audit endpoint)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/data/audit.test.ts

@@ -0,0 +1,58 @@
+import { describe, it, expect, beforeEach, afterEach } from "vitest";
+import { createDatabase, type BotDatabase } from "./database.js";
+import { createAuditStore, type AuditStore } from "./audit.js";
+
+describe("AuditStore", () => {
+  let botDb: BotDatabase;
+  let audit: AuditStore;
+
+  beforeEach(() => {
+    botDb = createDatabase(":memory:");
+    audit = createAuditStore(botDb.db);
+  });
+
+  afterEach(() => botDb.close());
+
+  it("records and lists entries newest-first", async () => {
+    audit.record({
+      actorId: "a1", actorUsername: "alice",
+      targetUserId: "b1", targetUsername: "bob",
+      action: "user.created",
+    });
+    await new Promise((r) => setTimeout(r, 5));
+    audit.record({
+      actorId: "a1", actorUsername: "alice",
+      targetUserId: "b1", targetUsername: "bob",
+      action: "user.deleted",
+    });
+    const list = audit.list(10, 0);
+    expect(list).toHaveLength(2);
+    expect(list[0].action).toBe("user.deleted");
+    expect(list[1].action).toBe("user.created");
+  });
+
+  it("supports limit and offset", () => {
+    for (let i = 0; i < 5; i++) {
+      audit.record({
+        actorId: "a1", actorUsername: "alice",
+        targetUserId: null, targetUsername: null,
+        action: "user.password_changed",
+      });
+    }
+    expect(audit.list(2, 0)).toHaveLength(2);
+    expect(audit.list(2, 4)).toHaveLength(1);
+    expect(audit.list(10, 10)).toHaveLength(0);
+  });
+
+  it("stores nullable fields correctly", () => {
+    audit.record({
+      actorId: null, actorUsername: null,
+      targetUserId: "x", targetUsername: "deleted-user",
+      action: "admin.first_created",
+    });
+    const e = audit.list(1, 0)[0];
+    expect(e.actorId).toBeNull();
+    expect(e.actorUsername).toBeNull();
+    expect(e.targetUserId).toBe("x");
+  });
+});