feat: add Groq Whisper API support for transcription and translation

Add support for Groq Whisper API as an alternative to OpenAI:
- groq-transcription: Fast transcription using whisper-large-v3 or whisper-large-v3-turbo
- groq-translation: Translation to English (whisper-large-v3 only)

Features:
- New transcription adapters for both Groq services
- Config validation with provider-specific model restrictions
- API key support via config file or GROQ_API_KEY environment variable
- Updated interactive configuration wizard with provider selection
- Comprehensive test coverage for all providers
- Shared WAV conversion utility for audio preprocessing

Breaking changes: None
Backward compatibility: Existing OpenAI configurations continue to work unchanged

internal/transcriber/transcriber.go

@@ -39,6 +39,18 @@ func NewTranscriber(config Config) (Transcriber, error) {
 		}
 		adapter = NewOpenAIAdapter(config)
 
+	case "groq-transcription":
+		if config.APIKey == "" {
+			return nil, fmt.Errorf("Groq API key required")
+		}
+		adapter = NewGroqTranscriptionAdapter(config)
+
+	case "groq-translation":
+		if config.APIKey == "" {
+			return nil, fmt.Errorf("Groq API key required")
+		}
+		adapter = NewGroqTranslationAdapter(config)
+
 	default:
 		return nil, fmt.Errorf("unsupported provider: %s", config.Provider)
 	}