Add explicit host validation to only allow audio output URLs from
replicate.delivery and its subdomains, blocking potential SSRF attacks
from malicious model outputs. Update tests to cover allowed and
disallowed host scenarios.
Adjust language input resolution in TTS generation to ensure Replicate Kokoro
model receives the appropriate language code mapping even when the language
property is absent or falsy. Update tests to cover this scenario and verify
correct input construction.
Implement logic to resolve and inject Replicate Kokoro model-specific language
codes based on language tag and voice, using new mapping utilities. Update
`buildReplicateInput` to set `language_code` for the built-in Kokoro model.
Expand language utilities with code mapping and expose `resolveReplicateKokoroLanguageCode`.
Enhance tests to cover language code resolution and input mapping for Replicate
Kokoro, and verify language input key discovery for built-in models.
