Fix role change silently failing via @bind

The role <select> used a manual value=/@onchange pattern that parsed
e.Value and returned silently when the parse failed, so changing a role
did nothing and showed no message. Switch to @bind + @bind:after so the
framework handles the enum conversion, and log/verify the persisted role
in UpdateRoleAsync (now returns the previous role) for diagnosis.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Components/Pages/Admin/UserManagement.razor

@@ -86,12 +86,11 @@ else
                         </td>
                         <td style="padding:8px">
                             <select class="form-input" style="width:130px"
-                                    value="@user.Role"
+                                    @bind="user.Role" @bind:after="() => PersistRoleAsync(user)"
-                                    @onchange="e => OnRoleChange(user, e)"
                                     disabled="@(user.Email == UserContext.Email)">
                                 @foreach (var role in Enum.GetValues<UserRole>())
                                 {
-                                    <option value="@role" selected="@(user.Role == role)">@role</option>
+                                    <option value="@role">@role</option>
                                 }
                             </select>
                         </td>
@@ -193,16 +192,14 @@ else
         }
     }
 
-    private async Task OnRoleChange(AppUser user, ChangeEventArgs e)
+    // Bound via @bind:after, so user.Role already holds the newly-selected value when this runs.
+    private async Task PersistRoleAsync(AppUser user)
     {
-        if (!Enum.TryParse<UserRole>(e.Value?.ToString(), out var newRole)) return;
         try
         {
-            var oldRole = user.Role;
+            var oldRole = await UserService.UpdateRoleAsync(user.Id, user.Role);
-            await UserService.UpdateRoleAsync(user.Id, newRole);
-            user.Role = newRole;
             await Audit.LogAsync("RoleChanged", "", Array.Empty<string>(),
-                $"Changed role for {user.Email} ({user.DisplayName}) from {oldRole} to {newRole}.");
+                $"Changed role for {user.Email} ({user.DisplayName}) from {oldRole} to {user.Role}.");
             _message  = string.Format(T["usermgmt.msg.roleupdated"], user.DisplayName);
             _isError  = false;
         }

Services/Auth/IUserService.cs

@@ -11,7 +11,9 @@ public interface IUserService
 
     Task<AppUser?> GetByEmailAsync(string email);
     Task<IReadOnlyList<AppUser>> GetAllAsync();
-    Task UpdateRoleAsync(string userId, UserRole role);
+    /// <summary>Persist a new role for the user. Returns the previous role (read from the store).</summary>
+    /// <exception cref="KeyNotFoundException">No user matches <paramref name="userId"/>.</exception>
+    Task<UserRole> UpdateRoleAsync(string userId, UserRole role);
     Task DeleteAsync(string userId);
 
     /// <summary>Create a local password-based account. First user ever becomes Admin.</summary>

Services/Auth/UserService.cs

@@ -1,5 +1,6 @@
 using System.Security.Claims;
 using Microsoft.AspNetCore.Identity;
+using Microsoft.Extensions.Logging;
 using SharepointToolbox.Web.Core.Models;
 using SharepointToolbox.Web.Infrastructure.Persistence;
 
@@ -9,11 +10,13 @@ public class UserService : IUserService
 {
     private readonly UserRepository _repo;
     private readonly IPasswordHasher<AppUser> _hasher;
+    private readonly ILogger<UserService> _logger;
 
-    public UserService(UserRepository repo, IPasswordHasher<AppUser> hasher)
+    public UserService(UserRepository repo, IPasswordHasher<AppUser> hasher, ILogger<UserService> logger)
     {
         _repo = repo;
         _hasher = hasher;
+        _logger = logger;
     }
 
     public async Task<AppUser> ProvisionAsync(ClaimsPrincipal principal)
@@ -56,13 +59,23 @@ public class UserService : IUserService
 
     public Task<IReadOnlyList<AppUser>> GetAllAsync() => _repo.LoadAsync();
 
-    public async Task UpdateRoleAsync(string userId, UserRole role)
+    public async Task<UserRole> UpdateRoleAsync(string userId, UserRole role)
     {
         var users = (await _repo.LoadAsync()).ToList();
         var user  = users.FirstOrDefault(u => u.Id == userId)
-                    ?? throw new KeyNotFoundException($"User {userId} not found.");
+                    ?? throw new KeyNotFoundException($"User '{userId}' not found among {users.Count} stored users.");
+
+        var oldRole = user.Role;
         user.Role = role;
         await _repo.UpsertAsync(user);
+
+        // Verify the write landed by re-reading the row from disk.
+        var persisted = (await _repo.LoadAsync()).FirstOrDefault(u => u.Id == user.Id)?.Role;
+        _logger.LogInformation(
+            "UpdateRoleAsync: {Email} (id {Id}) {OldRole} → {NewRole}; persisted value now {Persisted}.",
+            user.Email, user.Id, oldRole, role, persisted);
+
+        return oldRole;
     }
 
     public Task DeleteAsync(string userId) => _repo.DeleteAsync(userId);