feat: include history in export/import backup

Export now returns version 2 with a history array alongside instances.
Import accepts the history array and restores all audit events. v1 backups
without a history key still import cleanly.

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

tests/api.test.js

@@ -275,6 +275,18 @@ describe('GET /api/export', () => {
     const res = await request(app).get('/api/export')
     expect(res.body.instances).toEqual([])
   })
+
+  it('returns version 2', async () => {
+    const res = await request(app).get('/api/export')
+    expect(res.body.version).toBe(2)
+  })
+
+  it('includes a history array', async () => {
+    await request(app).post('/api/instances').send(base)
+    const res = await request(app).get('/api/export')
+    expect(res.body.history).toBeInstanceOf(Array)
+    expect(res.body.history.some(e => e.field === 'created')).toBe(true)
+  })
 })
 
 // ── POST /api/import ──────────────────────────────────────────────────────────
@@ -309,6 +321,26 @@ describe('POST /api/import', () => {
       .send({ instances: [{ ...base, name: undefined, vmid: 1 }] })
     expect(res.status).toBe(400)
   })
+
+  it('restores history when history array is provided', async () => {
+    await request(app).post('/api/instances').send(base)
+    const exp = await request(app).get('/api/export')
+    await request(app).post('/api/instances').send({ ...base, vmid: 999, name: 'other' })
+    const res = await request(app).post('/api/import').send({
+      instances: exp.body.instances,
+      history: exp.body.history,
+    })
+    expect(res.status).toBe(200)
+    const hist = await request(app).get('/api/instances/100/history')
+    expect(hist.body.some(e => e.field === 'created')).toBe(true)
+  })
+
+  it('succeeds with a v1 backup that has no history key', async () => {
+    const res = await request(app).post('/api/import')
+      .send({ instances: [{ ...base, vmid: 1, name: 'legacy' }] })
+    expect(res.status).toBe(200)
+    expect(res.body.imported).toBe(1)
+  })
 })
 
 // ── Static assets & SPA routing ───────────────────────────────────────────────