refactor: use dify_config to replace legacy usage of flask app's config (#9089)

api/extensions/storage/base_storage.py

@@ -3,16 +3,12 @@
 from abc import ABC, abstractmethod
 from collections.abc import Generator
 
-from flask import Flask
-
 
 class BaseStorage(ABC):
     """Interface for file storage."""
 
-    app = None
-
-    def __init__(self, app: Flask):
-        self.app = app
+    def __init__(self):  # noqa: B027
+        pass
 
     @abstractmethod
     def save(self, filename, data):