style: apply black and isort formatting across entire codebase

- Standardize quote style (single to double quotes)
- Reorder and group imports alphabetically
- Fix line breaks and indentation for consistency
- Apply PEP 8 formatting standards

Also updated Makefile to exclude both venv and .venv from code quality checks.

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Co-Authored-By: Claude <noreply@anthropic.com>

storage/backends.py

@@ -1 +1 @@
-# Storage backend implementations 
+# Storage backend implementations