Auto-delete assets and account data when a deletion-confirmed account is cleaned up

[oveldman]

Summary

Implements the automated account deletion cleanup flow (issue #172). When an administrator confirms an account deletion, a nightly background service (and a new manual trigger) now permanently removes the account's assets from object storage, hard-deletes all associated asset records and audit logs, and marks the account as Deleted — completing the full GDPR deletion lifecycle.

Changes

• Domain — added Account.Delete(clock) method with AccountErrors.DeletionNotConfirmed guard; added AccountDeletedEvent; added AuditErrors.DeleteFailed
• Application — added DeleteRequestedAccountsUseCase that processes all DeletionConfirmed accounts and dispatches AccountDeletedEvent; added AssetAccountEventHandler (deletes S3 content + asset records) and AuditAccountEventHandler (deletes audit logs) as domain event handlers
• Infrastructure — implemented IAccountRepository.GetConfirmedDeletionAccounts() and DeleteAsync(UserId); IAssetRepository.GetAssetsAsync(UserId), DeleteAsync(UserId), DeleteAsync(Asset); IAuditRepository.DeleteAsync(UserId)
• API — added POST /host-services/manual-triggers/clean-up/accounts manual trigger endpoint (Administrator policy)
• Hosted service — added DeleteRequestedAccountsService running daily at Cleanup:TriggerHourUtc
• Admin UI — added "Clean Up Deleted Accounts" card to the Manual Triggers page
• Tests — integration test covering the full cleanup flow (account + asset deletion); 6 component tests for all three manual trigger cards

How to Test

• Create an account via POST /accounts/me, request deletion via POST /accounts/me/deletion-request, confirm it via POST /accounts/{userId}/confirm-deletion
• Upload an asset under the same user before confirming deletion
• Call POST /host-services/manual-triggers/clean-up/accounts (requires Administrator JWT)
• Verify the account status is Deleted in the database and GET /assets/{id} returns 404 for the user's asset
• Alternatively run the integration test: dotnet test tests/MadWorldEU.Byakko.Controller.Api.IntegrationTests/ --filter "Manually trigger account deletion cleanup"

Checklist

• Code builds without errors
• Changes have been tested locally
• No new warnings introduced

[sonarqubecloud]

Quality Gate failed

Failed conditions
66.9% Coverage on New Code (required ≥ 80%)
5.2% Duplication on New Code (required ≤ 3%)

See analysis details on SonarQube Cloud