feat: [Indexer] Public http Endpoint

Design and implement the public endpoints for the indexer - The main challenge is what kind of authorization we are going to use for this as the indexer data is not public.

The issue names no files, tests, or existing entry points. Start by locating the indexer implementation and its HTTP surface, then clarify which public endpoints and authorization behavior are required. Done means the endpoint scope and access policy are agreed and implemented with coverage for authorized and unauthorized access.

Written by the indexing model from the issue text.