Add language dropdown with auto-detect and 26 languages

[PatelUtkarsh]

Summary

• Multilingual transcription support — users can select their spoken language in Settings for better accuracy and latency
• Auto-detect (default) — omits the language param, letting Whisper infer the language automatically
• 26 languages — English, Spanish, French, German, Italian, Portuguese, Dutch, Russian, Chinese, Japanese, Korean, Arabic, Hindi, Turkish, Polish, Swedish, Danish, Norwegian, Finnish, Czech, Ukrainian, Indonesian, Malay, Thai, Vietnamese, Gujarati

How it works

• TranscriptionLanguage enum with ISO-639-1 codes and a persisted UserDefaults preference
• When set to Auto-detect, the language field is omitted from the Groq API request entirely
• When a specific language is pinned, the ISO code is sent for improved accuracy and lower latency

Files changed

File	Change
GroqEngine.swift	Add TranscriptionLanguage enum, conditionally send language param
SettingsView.swift	Add language picker dropdown below model picker