Add PDF rendering support in Streamlit and Quarto reports

[Copilot]

VueGen had no support for PDF files as report components. This adds end-to-end PDF rendering: auto-detection from directory scans through to output code generation for both Streamlit and Quarto report types.

Changes

• report.py: Added PDF to PlotType enum
• config_manager.py: .pdf files are now auto-detected and configured as plot components with plot_type=pdf
• streamlit_reportview.py: Generates st.pdf() rendering code — reads bytes from local files or fetches from URLs via requests
• quarto_reportview.py: Adds _generate_pdf_content() that embeds PDFs via an HTML <iframe> (suitable for HTML/RevealJS output formats)

Example — generated Streamlit code for a local PDF

pdf_file_path = (section_dir / 'path/to/figure.pdf').resolve()
with open(pdf_file_path, 'rb') as pdf_file:
    pdf_data = pdf_file.read()
st.pdf(pdf_data, use_container_width=True)

For URL sources, the file is fetched via requests.get() and the response bytes are passed directly to st.pdf().