Push fails with HTTP 422 DataSyncError for invalid MBTiles file (zero-padded, 7.52 GB)

Description

When pushing a project containing an invalid MBTiles file (valid SQLite header, but ~7 GB of null bytes padding, czech.mbtiles) via the Mergin Maps QGIS plugin, the push fails with HTTP 422 DataSyncError.

Note: uploading the same file via the web dashboard (Files tab → Upload) succeeds without error.

Related: MerginMaps/python-api-client#303
Test data: https://drive.google.com/drive/folders/1qfp9ntxGJjbfKPu9_sY9fXVnSzb_T5Hc?usp=sharing

Environment
[x] Staging [ ] PROD

Application (+ app version, build, operating system)

• QGIS 3.44.7-Solothurn + Mergin Maps QGIS plugin d-146211
• macOS Tahoe 26.3

Steps to reproduce

1. Obtain or create an MBTiles file with a valid SQLite header but padded with ~7 GB of null bytes (total size ~7.52 GB)
2. Add the file to a Mergin Maps project in QGIS
3. Push the project via the Mergin Maps plugin

Actual results
Push fails with: "There are either corrupted files or it is not possible to create version with provided geopackage data" (HTTP 422, DataSyncError)

Expected results
TBD

Screenshots or logs

2026-06-18 20:57:27,319 --- push finish failed! Detail: There are either corrupted files or it is not possible to create version with provided geopackage data (DataSyncError) HTTP Error: 422 URL: https://app.dev.merginmaps.com/v2/projects/0b9bcb92-0cf2-44b2-99af-94230df3f995/versions Method: POST Error code: DataSyncError

Conclusion
Created by Claude and supervised by a human test analyst.

Start by reproducing the QGIS plugin push with the linked czech.mbtiles test data and compare it with the successful web dashboard upload. Read the related MerginMaps/python-api-client#303 issue and inspect the plugin's push flow around the HTTP 422 DataSyncError. Done should be defined after clarifying the currently TBD expected result, then covered by a regression test.