Release v0.3.1 - User Balance Top-Up

💰 Feature Enhancements

• User Balance Top-Up: Integrated increase_balance() and get_balance() in db/users.py alongside top_up_balance() in services/bookstore.py to allow users to add funds directly to their account.
• CLI Menu Update: Added Option 6. Top up balance to the main user menu.

🔄 Menu & UI Structure

• Option Renumbering: Shifted Option 6. Admin panel to Option 7. Admin panel to accommodate the top-up feature.

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Full Changelog: v0.3.0...v0.3.1