Add cancel deletion request for accounts

[oveldman]

Summary

Adds the ability for administrators to cancel a pending account deletion request, restoring the account to Active status. Also includes a GDPR user guide and documentation updates.

Changes

• Add CancelDeletion method to the Account domain entity
• Add CancelDeletionRequestAccountUseCase and POST /accounts/{userId}/cancel-deletion-request endpoint (Administrator policy)
• Add CancelDeletionRequestAsync to IAccountService and AccountService
• Add AccountCancelDeletionFailed to BlazorErrors
• Update Admin UI (AccountDeletionRequests.razor) with inline "Cancel request" action alongside "Confirm deletion"
• Fix Status/Updated column swap in the deletion requests table
• Add component tests for the cancel deletion flow
• Add GDPR user guide (docs/user-guides/Gpdr.md)
• Update docs/README.md and docs/index.md with new pages

How to Test

• Sign in to the Portal, go to Settings, and submit a deletion request
• Sign in to the Admin panel and open Accounts → Deletion Requests
• Verify the "Cancel request" button appears next to "Confirm deletion" for DeletionRequested accounts
• Click "Cancel request" → confirm the inline prompt → verify the account status returns to Active
• Verify that clicking "No" on the cancel prompt restores both action buttons without making an API call
• Verify that the "Confirm deletion" flow still works as before

Checklist

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

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
87.3% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud