Move os import to top-level imports

- Follow Python best practices by placing import at module level
- Remove redundant inline import from __init__ method

Co-Authored-By: João <joao@crewai.com>

lib/crewai/src/crewai/memory/storage/rag_storage.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import logging
+import os
 import traceback
 from typing import TYPE_CHECKING, Any, cast
 import warnings
@@ -49,7 +50,6 @@ class RAGStorage(BaseRAGStorage):
         self.allow_reset = allow_reset
         
         if path and path.strip():
-            import os
             self.path = os.path.abspath(path.strip())
         else:
             self.path = None