[WIP] Managing cross-project files (localized datasets)

[tdrivas]

trafficstars

This PR introduces two key updates to improve the handling of localized datasets in QFieldCloud projects:

1. Enhance process_projectfile to check for already localized dataset layers withing the organization.
2. Detect missing localized datasets and mark the corresponding projects as invalid.

Current Situation

• The process_projectfile job only handled project files without checking for cross-project dependencies.
• Projects continued processing even when required datasets were missing.

Actions to be implemented [ ] Modify the current API to serve localized datasets under a specific project [ ] Check if project contains all the required localized datasets ~[ ] Show the localized datasets related to a project under the project in the UI~ ~[ ] Make the changes compatible with the way QField consumes data.~