fix: whisper model billing

- Refactor model name handling across multiple controllers to improve clarity and maintainability.
- Enhance error logging and handling for better debugging and request processing robustness.
- Update pricing models in accordance with new calculations, ensuring accuracy in the billing logic.

common/ctxkey/key.go

@@ -21,4 +21,5 @@ const (
 	AvailableModels   = "available_models"
 	KeyRequestBody    = "key_request_body"
 	SystemPrompt      = "system_prompt"
+	Meta              = "meta"
 )