feat: harden bootstrap and add tests

tests/health-route.test.ts

@@ -0,0 +1,14 @@
+import { describe, expect, it } from 'vitest';
+import { GET } from '@/app/api/health/route';
+
+describe('/api/health', () => {
+  it('returns a fast healthy response', async () => {
+    const response = await GET();
+    const body = await response.json();
+
+    expect(response.status).toBe(200);
+    expect(body.ok).toBe(true);
+    expect(body.status).toBe('healthy');
+    expect(response.headers.get('cache-control')).toContain('no-store');
+  });
+});