Add CLI and Previous and Next Buttons in the Footer

[7174Andy]

This pull request introduces pagination support for viewing transactions in the Expense Tracker application, improves the organization and startup of the app, and adds a CLI entry point. The main changes include updating the repository and GUI to support paginated transaction lists, adding navigation controls, and improving test coverage for the new features.

Pagination and UI Enhancements:

• Added pagination to the transaction list in MainWindow, including "Previous" and "Next" buttons, page indicators, and logic to fetch only the relevant transactions per page (expense_tracker/gui/main_window.py). [1] [2] [3]
• Updated the repository to support paginated queries with limit and offset, and added a new count_all_transactions method to get the total number of transactions (expense_tracker/core/repository.py).

Application Structure and Entry Point:

• Improved the application startup by calling versions() at launch and updating the import path for MainWindow (expense_tracker/app.py). [1] [2]
• Added a CLI entry point for the app in pyproject.toml, enabling launch via expense-tracker command.

Testing:

• Added tests for the new count_all_transactions method to ensure correct behavior when adding and deleting transactions (tests/core/test_repository.py).