enh: chat share & export permissions

backend/open_webui/routers/users.py

@@ -88,6 +88,8 @@ class ChatPermissions(BaseModel):
     file_upload: bool = True
     delete: bool = True
     edit: bool = True
+    share: bool = True
+    export: bool = True
     stt: bool = True
     tts: bool = True
     call: bool = True