Scan list improvements

Reload scan thumbnail if modified date changes and show an "scan in progress" message for ongoing scans.

This again is going to be somewhat easier to understand/review commit by commit, the scan_list was becoming quite large and these changes would have made it larger still. Commit 2 broke out the scan card into its own component.

Closes #391 (closed)

Partial fix to #313 (closed)

This MR contains the following

• Remove commented out CSS
• Split ScanCards into their own Vue component
• Add the modified timestamp to the query for the thumbnail image, this means that the cached thumbnail isn't used if the scan is modified single last requested.
• Change scans endpoint to return an object with the list of scans and the name of the ongoing scan.
• Remove buttons (and any warnings about preview not being available) from scan card if the scan is ongoing.

Before

After

Merge checklist:

• All new/changed functions have up to date typehints and docstrings
• Any UI updates have a before and after screenshot in the MR description
• Unit testing of new functionality has similar or better coverage than similar existing code
• This code has been tested on a microscope
  • Webapp has been recompiled, with aesthetic changes checked in light and dark mode (if changed)
  • With updated settings JSON (if changed)
  • SmartScan and live stitching work