[S3] File changes are discarded if network connection is lost / timed out

[hcording]

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Summary

Note: not the same as #370

I edited a KeePassXC database in my vault, and after locking and exiting, Cryptomator showed the "Uploading File" Dialog. This was stuck at 0%, my internet connection was present but not very fast. After about a minute I got the error "No network connection", and I was not able to press retry or anything. After then trying to open the vault and the KeePass database again, Cryptomator just downloaded the server file, so my local changes were discarded, and I couldn't get them back. This could have ended very badly, especially with a password manger.

System Setup

- Android: 14 (Graphene OS)
- Cryptomator: 1.10.0
- Vault on Backblaze B2 bucket
- Keep vault open while editing enabled

Cloud Type

S3

Steps to Reproduce

1. Unlock the vault
2. Click the .kdbx database file, wait for it to load and the select KeePassXC in the "Open With" dialog
3. Make sure beyond this point your internet is slow or disconnected
4. Make some changes, save them in KeePassXC
5. Lock the database in KeePass: top left corner, burger menu, lock database
6. In the database selection screen that comes up, click the back arrow (top left corner)
7. Cryptomator should now show the Uploading File dialog
8. Wait for the "No network connection" error
9. Your changes are now lost and cannot be recovered

Expected Behavior

After the network error, I can click retry or something like "save local changes to a location of choice"

Actual Behavior

Changes are simply lost and cannot be recovered

Reproducibility

Always

Relevant Log Output

I'm not sure where to find this but I'd be happy to provide any logs with assistance.

Anything else?

Please note that this bug is extremely critical because it can lead to loss of very important data.