Centralize DB Handling to Decouple flexprep from Database Logic

To improve modularity, handle all database read/write operations in [the flex-container-orchestrator repo](https://github.com/MeteoSwiss/flex-container-orchestrator) so that flexprep doesn't need to interact with the DB directly. This will separate workflow logic from data handling, simplifying flexprep’s processing.

Start by reading the flexprep repository structure and the linked flex-container-orchestrator repository to identify where database reads and writes currently occur. Trace the workflow boundaries and document which operations must move; done means flexprep no longer interacts with the database directly and the orchestrator handles all database access.

Written by the indexing model from the issue text.