DOI downloads from sci-hub

When working with dt-mcp and interactively searching for scientific documents, you can now use the DOI to find your doc in DEVONthink or, when missing, download from sci-hub automatically.

• When searching for a scientific document by DOI, the AI first checks DEVONthink for existing copies
• If not found, uses sci-hub to download the PDF (tries multiple mirrors: sci-hub.se, .ru, .st, .ee, .ren)
• Parses the sci-hub page to extract the PDF URL (supports embed, iframe, onclick, object tags)
• Downloads the PDF and imports it into DEVONthink with metadata