feat: add provider interface and registry

internal/provider/openai.go

@@ -0,0 +1,42 @@
+package provider
+
+import "strings"
+
+// OpenAIProvider implements Provider for OpenAI services
+type OpenAIProvider struct{}
+
+func (p *OpenAIProvider) Name() string {
+	return "openai"
+}
+
+func (p *OpenAIProvider) RequiresAPIKey() bool {
+	return true
+}
+
+func (p *OpenAIProvider) ValidateAPIKey(key string) bool {
+	return strings.HasPrefix(key, "sk-")
+}
+
+func (p *OpenAIProvider) SupportsTranscription() bool {
+	return true
+}
+
+func (p *OpenAIProvider) SupportsLLM() bool {
+	return true
+}
+
+func (p *OpenAIProvider) DefaultTranscriptionModel() string {
+	return "whisper-1"
+}
+
+func (p *OpenAIProvider) DefaultLLMModel() string {
+	return "gpt-4o-mini"
+}
+
+func (p *OpenAIProvider) TranscriptionModels() []string {
+	return []string{"whisper-1"}
+}
+
+func (p *OpenAIProvider) LLMModels() []string {
+	return []string{"gpt-4o-mini", "gpt-4o", "gpt-4-turbo", "gpt-3.5-turbo"}
+}