Updated the UI across all screens (Login, Dashboard, Account Selection, Expense Details, and Creation) with a more modern, card-based design and improved layouts.
Expense creation now includes:
- Real-time split validation to ensure shares match the total amount.
- An "Equal Split" shortcut for quick allocation.
- Support for optional descriptions and multiple file attachments.
- Strict save validation.
The `MainActivity` now supports edge-to-edge display, and the `AccountDao` includes a new query to fetch accounts by ID. Added `material-icons-extended` dependency for enhanced iconography.