fix(llm): default model slug free/gemini-3.8-flash (billing)

apinex_client.py

@@ -96,7 +96,7 @@ TONE_PROFILE_SYSTEM_PROMPT = """Составь или обнови единый
 """
 
 
-def _setting(name: str, default: str = "gemini-3.8-flash") -> str:
+def _setting(name: str, default: str = "free/gemini-3.8-flash") -> str:
     return os.getenv(name, "").strip() or default