Add sort_by_date_modified parameter to all search endpoints

[Srijatalamarla]

Change(s)

Change Type: Added

Change Category: Interface

Changelog Entry: Added sort_by_date_modified boolean parameter to all search endpoints.
When set to true, results are sorted by date modified descending ( newest first ). By default, results are sorted based on relevance score.

Checklist

• Tests have been added or updated to reflect the changes, or their absence is explicitly explained.
• Documentation has been added or updated to reflect the changes, or their absence is explicitly explained.
• A self-review has been conducted checking:
  • No unintended changes have been committed.
  • The changes in isolation seem reasonable.
  • Anything that may be odd or unintuitive is provided with a GitHub comment explaining it (but consider if this should not be a code comment or in the documentation instead).
• All CI checks pass before pinging a reviewer, or provide an explanation if they do not.
• The PR title matches the changelog entry's one-line description.

Related Issues

Closes #521