feat(api): implement notebook management CRUD endpoints

Implement Sprint 1: Notebook Management CRUD

- Add NotebookService with full CRUD operations
- Add POST /api/v1/notebooks (create notebook)
- Add GET /api/v1/notebooks (list with pagination)
- Add GET /api/v1/notebooks/{id} (get by ID)
- Add PATCH /api/v1/notebooks/{id} (partial update)
- Add DELETE /api/v1/notebooks/{id} (delete)
- Add Pydantic models for requests/responses
- Add custom exceptions (ValidationError, NotFoundError, NotebookLMError)
- Add comprehensive unit tests (31 tests, 97% coverage)
- Add API integration tests (26 tests)
- Fix router prefix duplication
- Fix JSON serialization in error responses

BREAKING CHANGE: None

tests/unit/test_api/test_health.py

@@ -0,0 +1,56 @@
+"""Tests for health routes."""
+
+import pytest
+from fastapi.testclient import TestClient
+
+from notebooklm_agent.api.main import app
+
+
+@pytest.mark.unit
+class TestHealthEndpoints:
+    """Test suite for health check endpoints."""
+
+    def test_health_check_returns_healthy(self):
+        """Should return healthy status."""
+        # Arrange
+        client = TestClient(app)
+
+        # Act
+        response = client.get("/health/")
+
+        # Assert
+        assert response.status_code == 200
+        data = response.json()
+        assert data["status"] == "healthy"
+        assert "timestamp" in data
+        assert data["service"] == "notebooklm-agent-api"
+        assert data["version"] == "0.1.0"
+
+    def test_readiness_check_returns_ready(self):
+        """Should return ready status."""
+        # Arrange
+        client = TestClient(app)
+
+        # Act
+        response = client.get("/health/ready")
+
+        # Assert
+        assert response.status_code == 200
+        data = response.json()
+        assert data["status"] == "ready"
+        assert "timestamp" in data
+        assert "checks" in data
+
+    def test_liveness_check_returns_alive(self):
+        """Should return alive status."""
+        # Arrange
+        client = TestClient(app)
+
+        # Act
+        response = client.get("/health/live")
+
+        # Assert
+        assert response.status_code == 200
+        data = response.json()
+        assert data["status"] == "alive"
+        assert "timestamp" in data