BI-2964: BrAPI Observation GET: Apply pagination and filtering on BrAPI side

[humsika]

Description

Story - BI-2964
Fixed an edge case in BrAPI pagination where the first invalid page returned 200 OK when the total record count was exactly divisible by the page size. The shared validator now correctly returns 400 Bad Request when page >= totalPages.

Dependencies

bi-web: epic/BI-2862
bi-api: feature/BI-2964
brapi-Java-ProdServer: feature/BI-2964

Testing

• Open Experiments & Observations and select an experiment containing observations.
• Verify that the observations load successfully.
• Apply filters and confirm the displayed observations match the selected filters.
• Navigate between different pages and confirm the correct data loads on each page without errors.
• Change the page size, if available, and confirm pagination continues to work 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