Issue 1: Migrate active database out of legacy resource group

### Background
The authentication related web pages have been reorganized and moved to access management frontend. Therefore authenticationui-xxx-rg esource group is scheduled for teardown, but it still contains one active database that must be preserved.

### Tasks
- [x] Target resource group for the database - altinnplatform-xxx-rg
- [x] Verify all consumers/connection strings pointing to the database
- [x] Move the database to the target resource group
- [x] Update connection strings, Key Vault references, and app settings in dependent services
- [x] Verify connectivity and run smoke tests after the move
- [x] Confirm backups/retention policies carry over in the new resource group

Review the target resource group, active database, dependent services, connection strings, Key Vault references, and app settings described in the issue. No files or specific tests are named; done means the database is preserved in altinnplatform-xxx-rg, consumers remain connected, smoke tests pass, and backup and retention policies are confirmed.

Written by the indexing model from the issue text.