* feat: enhance invoice management and immutability checks
- Update InvoiceDetailPage to prevent deletion of drafts with assigned invoice numbers, providing user feedback.
- Modify the invoice conversion API to ensure invoice number allocation occurs only after successful item insertion and proforma cancellation.
- Implement structured error responses for invoice deletion, ensuring only drafts without assigned numbers can be deleted.
- Add comprehensive tests for invoice deletion and conversion scenarios, including edge cases for draft invoices.
- Introduce immutability checks in the document management system to prevent unauthorized changes to linked documents.
- Create SQL migration to enforce document metadata immutability, ensuring compliance with accounting regulations.
* fix(invoice): prevent invoice number consumption on PDF render failure
* feat: add document journal entry immutability enforcement for delete_last_voucher RPC
* fix(invoice): implement rollback for orphan invoices on proforma cancel failure
* fix(document): extend immutability trigger to protect journal entry links