Feature Request: Add language configuration for /voice mode (Portuguese support)

Feature Request

Description

The /voice command currently defaults to English for speech-to-text, with no option to configure the input language. Users who work primarily in other languages (e.g., Brazilian Portuguese) cannot use voice mode effectively.

Proposed Solution

Add a voiceLanguage setting (or similar) to settings.json that allows users to configure the speech-to-text language for /voice mode. For example:

{
  "language": "Português Brasileiro",
  "voiceLanguage": "pt-BR"
}

Ideally, if voiceLanguage is not set, it could fall back to the existing language setting.

Use Case

• I work in a Portuguese-speaking environment and all my documentation, code comments, and team communication are in Brazilian Portuguese
• The language setting already makes Claude respond in Portuguese, but voice input still only recognizes English
• Being able to speak in Portuguese would make the voice mode actually usable for non-English speakers

Additional Context

• The language setting already exists and works for text responses — extending this to voice would be a natural progression
• This would benefit all non-English speaking users, not just Portuguese speakers
• Related issue: #31724