enh: enable configuration for tavily extract depth

backend/open_webui/config.py

@@ -1950,6 +1950,12 @@ TAVILY_API_KEY = PersistentConfig(
     os.getenv("TAVILY_API_KEY", ""),
 )
 
+TAVILY_EXTRACT_DEPTH = PersistentConfig(
+    "TAVILY_EXTRACT_DEPTH",
+    "rag.web.search.tavily_extract_depth",
+    int(os.getenv("TAVILY_EXTRACT_DEPTH", "basic")),
+)
+
 JINA_API_KEY = PersistentConfig(
     "JINA_API_KEY",
     "rag.web.search.jina_api_key",