Address lint failures and improve exception handling

- Remove unused imports (os from rag_storage.py, pytest from test_memory_fallback.py)
- Add specific exception handling in fallback mechanism (ConnectionError, ImportError, ValueError)
- Add comprehensive logging to track embedding provider selection and fallback attempts
- Resolves CI lint failures and addresses PR review feedback

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

tests/test_memory_fallback.py

@@ -1,5 +1,4 @@
 import os
-import pytest
 from unittest.mock import patch
 
 from crewai import Agent, Task, Crew, Process