[WIP] Flask3 migration, general cleanup

[LincolnBryant]

Short summary of changes

• Ran pylint everywhere, with a goal of getting to a score of at least 5/10 on every file 😮‍💨
• Ran black everywhere
• Upgrade Flask to v3, from v1
• Upgrade bootstrap from v5 from v3
• Upgrade jquery from v3.7 from v3.3
• Try to normalize return types where possible and encapsulate requests to clean up some code smell
• Add request timeout everywhere (cleanup TBD). Default of 10s. This will occasionally cause failures to retrieve data but it shouldn't cause indefinite hangs or crashes.