feat: Style sales and purchases forms - 80% progress.
feat: Validate purchase-able and sell-able items in invoices and bills.
feat: Fix bugs in inventory FIFO/LIFO cost methods.
- fix: store expense payment date with transactions.
- fix: Total assets, liabilities and equity on balance sheet.
- tweaks: dashboard content and sidebar style.
- fix: reset form with contact list on journal entry form.
- feat: Add hints to filter accounts in financial statements.