Allow editing orders in the order card

Cashiers can edit recipient, TTN, notes, goods and total in the order
modal and save via PATCH /orders/{id}. Edited orders get edited_at and
are no longer overwritten by CRM sync. Editing is blocked once a receipt
exists; changing the TTN resets Nova Poshta tracking fields.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

backend/app/db/models/audit.py

@@ -32,6 +32,7 @@ class AuditAction(str):
     USER_UPDATED = "user.updated"
     USER_DEACTIVATED = "user.deactivated"
     ORDER_DELETED = "order.deleted"
+    ORDER_UPDATED = "order.updated"
     CASH_REGISTER_CREATED = "cash_register.created"
     CASH_REGISTER_UPDATED = "cash_register.updated"
     RECEIPT_CREATE_REQUESTED = "receipt.create_requested"