feat(video-lab): /api/internal/video/update endpoint + tests (SP-8)

UpdatePayload schema (task_id/status/progress/message/video_url/error).
404 if task not found. insta/music-lab과 동일 패턴 + video_url 필드.
Plan-B-Video Phase 1.

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

video-lab/tests/test_internal_router.py

@@ -0,0 +1,89 @@
+"""POST /api/internal/video/update — Windows video-render webhook."""
+import pytest
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+from app.internal_router import router
+from app import db
+
+
+@pytest.fixture(autouse=True)
+def _set_key(monkeypatch):
+    monkeypatch.setenv("INTERNAL_API_KEY", "test-secret")
+
+
+@pytest.fixture
+def client(tmp_path, monkeypatch):
+    monkeypatch.setenv("VIDEO_DATA_DIR", str(tmp_path))
+    monkeypatch.setattr(db, "DB_PATH", str(tmp_path / "test_video.db"))
+    db.init_db()
+    app = FastAPI()
+    app.include_router(router)
+    return TestClient(app)
+
+
+def _make_task():
+    tid = "video-task-1"
+    db.create_task(tid, "sora", {"prompt": "test"})
+    return tid
+
+
+def test_update_with_valid_key_updates_db(client):
+    tid = _make_task()
+    r = client.post(
+        "/api/internal/video/update",
+        headers={"X-Internal-Key": "test-secret"},
+        json={"task_id": tid, "status": "processing", "progress": 30, "message": "downloading"},
+    )
+    assert r.status_code == 200
+    task = db.get_task(tid)
+    assert task["status"] == "processing"
+    assert task["progress"] == 30
+    assert task["message"] == "downloading"
+
+
+def test_update_with_invalid_key_returns_401(client):
+    tid = _make_task()
+    r = client.post(
+        "/api/internal/video/update",
+        headers={"X-Internal-Key": "wrong"},
+        json={"task_id": tid, "status": "processing", "progress": 30},
+    )
+    assert r.status_code == 401
+
+
+def test_update_succeeded_with_video_url(client):
+    tid = _make_task()
+    r = client.post(
+        "/api/internal/video/update",
+        headers={"X-Internal-Key": "test-secret"},
+        json={
+            "task_id": tid, "status": "succeeded", "progress": 100,
+            "message": "완료", "video_url": "/media/video/video-task-1.mp4",
+        },
+    )
+    assert r.status_code == 200
+    task = db.get_task(tid)
+    assert task["status"] == "succeeded"
+    assert task["video_url"] == "/media/video/video-task-1.mp4"
+
+
+def test_update_failed_records_error(client):
+    tid = _make_task()
+    r = client.post(
+        "/api/internal/video/update",
+        headers={"X-Internal-Key": "test-secret"},
+        json={"task_id": tid, "status": "failed", "progress": 0, "error": "Sora API rate limit"},
+    )
+    assert r.status_code == 200
+    task = db.get_task(tid)
+    assert task["status"] == "failed"
+    assert "Sora" in (task.get("error") or "")
+
+
+def test_update_unknown_task_returns_404(client):
+    r = client.post(
+        "/api/internal/video/update",
+        headers={"X-Internal-Key": "test-secret"},
+        json={"task_id": "nonexistent", "status": "processing", "progress": 10},
+    )
+    assert r.status_code == 404