feat: Enhance invoice file backup procedure to include JSON snapshots

- Updated the stored procedure `fds__admin_backupAndClearInvoiceFile.sql` to back up not only the invoice file but also JSON snapshots of related data (invoices, items, details, service requests) to ensure consistency and traceability.
- Modified the table structure of `fds__invoice_file_backups` to accommodate new JSON columns for storing these snapshots.
- Added an ADR (0030) document to outline the decision and rationale behind these changes, emphasizing the importance of maintaining a consistent set of data alongside the backed-up file.

Fuchs.Tests/ProcessWebComServiceTests.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Diagnostics.Metrics;
 using System.IO;