Locations: DB Model update & migration to add location table

[samturner3]

It would be great to have 'location' as a separate table, rather than string on a spool.

This will allow us to print labels for locations, then scan a QR code label for a location and see what spools are in said location.

To do:

• [x] Update DB model to include a new 'location' table

• [x] Add a migration file to migrate existing locations (in spool) to create new locations and handle non-unique names etc.

• [ ] Add UI screens for location model - including update spool location UI

• [ ] Add a locations page - include view to see list of all spools in a location

• [ ] Re-arrange spools between locations UI (drag and drop?) (stretch goal)

• [ ] Add ability to print labels with QR codes for locations - upon scan show view to see list of all spools in a location

• [ ] Update tests

• [ ] Add test for migration to ensure existing string spool.location create a location object successfully. (Tested and passed manually)

Feedback as I go would be appreciated with and concerns / requests. See https://github.com/Donkie/Spoolman/discussions/465 - please provide your thoughts