feat: add pagination metadata to API responses (#630)

[heisdinesh]

Change(s)

Change Type: Added / Changed

Change Category: Interface

Changelog Entry: Added pagination metadata to API responses (#630)

Introduced a PaginatedResponse model that wraps paginated array results. Endpoints serving paginated data (such as resource lists, platforms, and bookmarks) now return a JSON object containing offset, limit, total_count, and the actual array of results in a data field. This allows clients to understand the total number of items available for pagination.

How to Test

Perform a GET request on any paginated endpoint, for example /platforms or /datasets/v1 with a limit and offset.
Verify that the response is no longer a top-level list, but a JSON dictionary matching this structure:

{
  "offset": 0,
  "limit": 10,
  "total_count": 42,
  "data": [
    ...
  ]
}

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 #630

[heisdinesh]

Hey @PGijsbers could you review this PR.