Normalize request from frontend

Identify type of AOI (eg. linework, kml, query) and normalize to go into AOI builder.
What will request from frontend look like?

Can get by without this for testing purposes

Web-based front-end will take care of some validation that might happen here (eg. valid geometry)

Start by clarifying the frontend request shape and the AOI builder entry point; the issue provides no file or test paths. Define how linework, KML, and query inputs are identified and normalized, then confirm the resulting request is accepted by the builder while leaving frontend geometry validation out of scope.

Written by the indexing model from the issue text.