Rename snake_case query parameters to camelCase

[ExtraToast]

What to build

This service's query parameters are renamed to camelCase, matching every other service in the estate.

It is currently the only service using snake_case parameter names, which is why the estate cannot yet enforce a casing rule. This is a breaking contract change: it takes the generated clients to a new major version and every consumer must move in step.

Acceptance criteria

• No query or path parameter uses snake_case
• The breaking change is landed deliberately, with the client major bump expected rather than surprising
• Every consumer of the renamed parameters is updated
• Export drift passes

Blocked by

• Adopt the ProblemDetail customizer and re-export the spec