BI-2920: Study Cache 3 - Update bi-web StudyData tables if necessary

[humsika]

Description

Story: BI-2920

Update the bi-web Study flow to use BrAPI database IDs.

• Changed the Study lookup from the Trial external-reference ID to trialDbId.
• Changed environment selection/export to use studyDbId.
• Removed unused external-reference lookup code.

Dependencies

bi-web: feature/BI-2920
bi-api: epic/BI-2862
brapi-Java-ProdServer: epic/BI-2862

Testing

• Open an experiment and its download modal.
• Verify the /studies request uses trialDbId.
• Verify it does not send externalReferenceId or externalReferenceSource.
• Select one environment and verify the export uses its studyDbId.
• Verify single- and all-environment downloads contain the correct data.
• Verify the Study Data table continues to display Observation Units and observations correctly.

Checklist:

• I have performed a self-review of my own code
• I have tested my code and ensured it meets the acceptance criteria of the story
• I have commented my code, particularly in hard-to-understand areas
• I have either updated the source of truth or arranged for update with product owner if needed https://breedinginsight.atlassian.net/wiki/spaces/BI/pages/1559953409/Source+of+Truth
• I have run SiteImprove on pages impacted by changes