feat: implement admin action APIs for comment and profile moderation

Added full API implementation for admin action buttons in the report
management interface:

Backend Changes:
- Created new /api/comments routes for admin-only comment operations
- Added PUT /api/comments/:id for admin comment editing
- Added DELETE /api/comments/:id for admin comment deletion
- Added POST /api/users/:id/make-private for admin profile privacy control
- All endpoints protected with adminGuard and csrfProtection
- Proper audit logging for all admin actions
- Added onDelete: Cascade to CommentReport relation for safe comment deletion

Frontend Changes:
- Added adminUpdateComment() and adminDeleteComment() to CommentsService
- Added makeProfilePrivate() to UserService
- Integrated API calls into admin-reports component methods
- editComment() now updates comment via API and refreshes report list
- deleteComment() now deletes comment via API and refreshes report list
- makeProfilePrivate() now updates profile privacy via API
- editProfile() navigates using ObjectId instead of Discord username
- All actions show success/error toasts and close modals on completion

The admin interface now has full working moderation capabilities for both
comment and profile reports.

apps/frontend/src/app/services/user.service.ts

@@ -81,4 +81,8 @@ export class UserService {
   getProfile(identifier: string): Observable<UserProfileResponse> {
     return this.api.get<UserProfileResponse>(`/users/profile/${identifier}`);
   }
+
+  makeProfilePrivate(userId: string): Observable<User> {
+    return this.api.post<User>(`/users/${userId}/make-private`, {});
+  }
 }