Relocate Hit Highlighting Feature from finesse-frontend to finesse-backend

[k-allagbe]

The goal is to centralize the hit highlighting process for non-Azure sources in finesse-backend, aligning with the existing Azure source handling. This shift aims to unify the logic, ensuring consistency across different sources.

Tasks:

1. Develop hit highlighting logic in the backend for non-Azure sources.
2. Adjust the frontend to fetch highlighted content from the backend.
3. Conduct tests to verify that the backend's highlighting aligns with current standards.
4. Update relevant documentation to reflect the backend-centric approach.

Acceptance Criteria:

• Backend handles hit highlighting for all sources uniformly.
• Frontend correctly displays highlighted content from the backend.
• Consistent highlighting results across Azure and non-Azure sources.
• All tests confirm the new implementation's reliability.
• Documentation accurately describes the unified highlighting approach.