Add endpoint /api/v1/seqvars/annos/query with OpenAPI schema

[holtgrewe]

Is your feature request related to a problem? Please describe.
We currently have an endpoint /annos/variant that does not have an OpenAPI schema. Also, it does not live under a proper version namespace.

Describe the solution you'd like
Create a new endpoint with equivalent functionality at the given path. Ensure query and response are properly (de)serializable with Utoipa.

Describe alternatives you've considered
N/A

Additional context
N/A