micro-fix: add missing __init__.py to file_system_toolkits

[kurtjallo]

Summary

• Adds missing __init__.py to tools/src/aden_tools/tools/file_system_toolkits/ for consistent package structure

Closes #6055

[github-actions]

PR Requirements Warning

This PR does not meet the contribution requirements.
If the issue is not fixed within ~24 hours, it may be automatically closed.

PR Author: @kurtjallo
Found issues: #6055 (assignees: none)
Problem: The PR author must be assigned to the linked issue.

To fix:

1. Assign yourself (@kurtjallo) to one of the linked issues
2. Re-open this PR

Exception: To bypass this requirement, you can:

• Add the micro-fix label or include micro-fix in your PR title for trivial fixes
• Add the documentation label or include doc/docs in your PR title for documentation changes

Micro-fix requirements (must meet ALL):

Qualifies	Disqualifies
< 20 lines changed	Any functional bug fix
Typos & Documentation & Linting	Refactoring for "clean code"
No logic/API/DB changes	New features (even tiny ones)

Why is this required? See #472 for details.