API: filter GET /v1/voices by type, locale, gender, and model

API: filter `GET /v1/voices` by type, locale, gender, and model

GET /v1/voices now accepts four optional query filters:

Filter	Values	Description
`type`	`personal`, `shared`	`personal` (the workspace’s cloned voices) or `shared` (the public catalogue). Omit to return both.
`locale`	BCP-47 range	Prefix-matched and case-insensitive: `en` matches `en-US` and `en-GB`; `en-US` matches only `en-US`.
`gender`	`male`, `female`, `not_specified`	Omit to return all genders.
`model`	a model id, e.g. `simba-3.2`	Voices that advertise the model in their `models[]`. Omit to return voices for all models.

For example, fetch the catalogue voices that speak English and support simba-3.2:

$ curl "https://api.speechify.ai/v1/voices?type=shared&locale=en&model=simba-3.2" \
>   -H "Authorization: Bearer $SPEECHIFY_API_KEY"

Filters compose with pagination: pass limit (max page size 200) and page with cursor, reading until has_more is false.