Implement cascading deletion of user roles and edits with project visibility

[Copilot]

User deletion left orphaned UserRole and UserEdit records in the database. The deletion dialog provided no visibility into which projects would be affected.

Backend Changes

• UserController: Enhanced DeleteUser to cascade delete all associated UserRole and UserEdit records. Added validation to prevent admin user deletion (returns 403).
• New endpoint: GET /v1/users/{userId}/projects returns project names and roles for deletion confirmation.
• UserProjectInfo DTO: Simple model containing projectId, projectName, and role.

// Cascade deletion implementation
foreach (var (projectId, userRoleId) in user.ProjectRoles)
    await _userRoleRepo.Delete(projectId, userRoleId);

foreach (var (projectId, userEditId) in user.WorkedProjects)
    await _userEditRepo.Delete(projectId, userEditId);

Frontend Changes

• ConfirmDeletion dialog: Fetches and displays user's project memberships with roles before deletion. Shows loading/error states appropriately.
• backend/index.ts: Added getUserProjects() function and UserProjectInfo interface.

Tests

Added 5 test cases covering:

• Cascading deletion of roles and edits
• Admin user deletion prevention
• Project listing endpoint (happy path, auth, not found)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>DeleteUser should interact with project roles and user edits</issue_title>
<issue_description>A site admin, from site settings can delete any non-admin user. Several issues:

• There's a dialog confirming deletion, but no warnings what projects the user is on or what edits they have
• When the user is deleted, their user roles and user edits are orphaned in the database
• The frontend gui prevents admins from deleting other admins, but the backend controller doesn't prevent it

Currently it requires a maintenance script to delete projects and the script handles all the cleanup. Perhaps it should be the same with users. From the gui, would we want the ability to disable accounts instead of deleting them (like archiving a project)?

Todo:

• In the confirm-deletion dialog, list projects the user is in and what their role is in each project.
• When the user is deleted, also:
  • delete all their user roles
  • update the projects to remove those roles
  • delete all the user edits</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes DeleteUser should interact with project roles and user edits #3875

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This change is 

[github-actions]

⚠️ Commit Message Format Issues ⚠️
commit c84025e3c1:
1: T1 Title exceeds max length (74>72): "Add frontend support for displaying user projects in deletion confirmation"

[codecov]

Codecov Report

❌ Patch coverage is 71.23288% with 21 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.36%. Comparing base (0298e39) to head (c209918).

Files with missing lines	Patch %	Lines
...ts/SiteSettings/UserManagement/ConfirmDeletion.tsx	0.00%	20 Missing ⚠️
Backend/Controllers/UserController.cs	98.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3971      +/-   ##
==========================================
- Coverage   74.40%   74.36%   -0.04%     
==========================================
  Files         291      291              
  Lines       10790    10862      +72     
  Branches     1351     1360       +9     
==========================================
+ Hits         8028     8078      +50     
- Misses       2373     2393      +20     
- Partials      389      391       +2     

Flag	Coverage Δ
backend	85.57% <98.11%> (+0.11%)	⬆️
frontend	65.65% <0.00%> (-0.22%)	⬇️

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