Rewrite database backend (JSON File -> SQLite)

[Capevace]

The current database backend of saving everything to a database.json file is not really nice nor safe.

• [ ] Rewrite backend to use SQLite
  • [ ] Default data insertion
  • [ ] Database migrations
  • [ ] Store uploaded files in SQLite
  • [ ] Store sessions in SQLite
  • [ ] .mission-control folder should then only have config file and database.sqlite file