Set a custom starting invoice number

Allow users to set the starting invoice number for their workspace, so anyone migrating from another invoicing system (or continuing a long-running numbering sequence) can preserve continuity. Example: a freelancer is currently at invoice 600 in their previous system. When they switch to HoneyBill, the next invoice should be 601, not 1, so their accountant and audit trail stay clean. Useful for: - Migrating from another invoicing tool (FreshBooks, QuickBooks, Xero, spreadsheets, etc.) - Continuing an existing numbering sequence after reincorporation or rebrand - Resetting numbering at the start of a financial year Worth considering alongside: the ability to edit the number on a specific invoice if the sequence needs a one-off adjustment.