Add integration tests for PDF viewer flow

[cbcoutinho]

Problem

Excellent unit tests exist, but no integration tests verifying:

• End-to-end flow: Vue component → PHP controller → Python API → WebDAV download → PyMuPDF render
• Actual PDF rendering with different PDF types
• Page navigation in the UI

Recommendation

Add integration test in tests/integration/test_astrolabe_pdf_viewer.py:

@pytest.mark.integration
async def test_pdf_viewer_end_to_end(nc_mcp_oauth_client, nc_client):
    """Test complete PDF viewing flow through Astrolabe UI."""
    # 1. Upload test PDF via WebDAV
    # 2. Index it via vector sync (or skip if not needed)
    # 3. Request PDF preview via API
    # 4. Verify base64 image is valid PNG
    # 5. Verify page navigation works
    ...

Location

• tests/integration/

Priority

Nice to have - Improves confidence in end-to-end flow

Parent Issue

Part of #502