fix/sync error cleanup

[juliushaertl]

• Refactor the general sync state into a defined data strcuture by splitting push/sync/save state and also remembering last success/failure time, number of failures. That way we have more control to show errors only if the issue persists and not immediately on flaky connections
• Indicate that local changes were not pushed to the server with a proper error message on the save indicator
  • Figure out if we can auto retry the push or if we want to let the user manually trigger it
• Avoid immediately setting the editor to read only
• Avoid saving the file as the user if there are unpushed steps
• Warn users when navigating away with unpushed steps
• File follow up issue for proper offline support, keeping changes in the browser storage and pushing later

📝 Summary

• Resolves: #

🖼️ Screenshots

🏚️ Before	🏡 After
B	A

🚧 TODO

• ...

🏁 Checklist

• Code is properly formatted (npm run lint / npm run stylelint / composer run cs:check)
• Sign-off message is added to all commits
• Tests (unit, integration and/or end-to-end) passing and the changes are covered with tests
• Documentation (README or documentation) has been updated or is not required

[juliushaertl]

Closing until further discussed during the contributor week