Complete type-hinting across all scripts

[jsvine]

Running mypy ./scripts --ignore-missing-imports --strict suggests these are the scripts I need to add type-hinting to:

• [x] 00-fetch-inspection-list.py
• [x] 01-refresh-inspection-list.py
• [x] 02-download-inspection-pdfs.py
• [x] 04-upload-inspection-pdfs.py