- Overlay if substitutions / history view is still loading
- Overlay if no substitution exists for current day
- Overlay if no history exists for current day
- Move view related functions out of the store
- Restructure the store.js file
- Improve error handling of `/check`
- Show red loading spinner if data fetch failed
- Prefetch current, next and previous day instead of only current
- Refactor some other frontend file
