Add /stop/routes endpoint

[Jouca]

This PR proposes a new endpoint /v1/stop/routes, designed to retrieve all routes serving a specific stop. This approach avoids relying on other endpoints (notably /stoptimes) to infer which routes pass through a stop, providing a more direct, efficient, and optimized solution.

It follows discussion #742, which suggested introducing a dedicated endpoint to fetch routes from a stop. The current implementation focuses solely on stops and does not fully address all aspects of the original proposal. In particular, a more comprehensive solution could also consider a feed-level perspective, potentially through a separate endpoint (e.g., /v5/routes).

Parameters for /v1/stop/routes:

Name	Type	Required	Default	Description
stopId	string	no¹	—	Stop ID as returned by /api/v1/geocode or /api/v1/map/stops
center	string	no¹	—	latitude,longitude pair used as center for a radius search
radius	integer	no	500	Search radius in meters around center
language	string[]	no	—	Language preference for translated names (BCP-47, e.g. en, fr, de)

¹ Either stopId or center must be provided.

Examples

GET /api/v1/stop/routes?stopId=fr-idf_IDFM:71264
GET /api/v1/stop/routes?center=48.8566,2.3522&radius=300
GET /api/v1/stop/routes?stopId=fr-idf_IDFM:71264&language=fr

[Jouca]

Fixed formatting & errors, ready for a workflow run

[Jouca]

Should be fixed again, ready for a workflow run