fix(server): proper asset sync

[fyfrey]

fixes #9534 and bunch of other issues

breaking change! app and server must be on same version to work

with this change:

1. the server full sync method always returns the exact number of requested assets (unless it is the last chunk)
2. sync methods load the stacked asset count in a follow-up query via loadRelationCountAndMap so that limit works correctly
3. the app stops the fetching for more assets when the first non-full chunk is received
4. syncing uses id instead of fileCreatedAt because it may have weird metadata issues.

[alextran1502]

Cloning my prod instance tonight to test this in the morning! For science!!!

[danieldietzler]

Server code looks good to me!