Add remember username on login

src/dotnet/QuantEngine.Web/Client/Infrastructure/CustomAuthenticationStateProvider.cs

@@ -12,6 +12,7 @@ namespace QuantEngine.Web.Client.Infrastructure
         private const string TokenKey = "quant_admin_access_token";
         private const string UsernameKey = "quant_admin_username";
         private const string RoleKey = "quant_admin_role";
+        private const string RememberUsernameKey = "quant_admin_remember_username";
 
         public CustomAuthenticationStateProvider(LocalStorageService localStorage, HttpClient http)
         {
@@ -57,9 +58,23 @@ namespace QuantEngine.Web.Client.Infrastructure
         }
 
         public async Task MarkUserAsAuthenticatedAsync(string username, string accessToken, string role)
+        {
+            await MarkUserAsAuthenticatedAsync(username, accessToken, role, rememberUsername: true);
+        }
+
+        public async Task MarkUserAsAuthenticatedAsync(string username, string accessToken, string role, bool rememberUsername)
         {
             await _localStorage.SetAsync(TokenKey, accessToken);
-            await _localStorage.SetAsync(UsernameKey, username);
+            if (rememberUsername)
+            {
+                await _localStorage.SetAsync(UsernameKey, username);
+                await _localStorage.SetAsync(RememberUsernameKey, true);
+            }
+            else
+            {
+                await _localStorage.DeleteAsync(UsernameKey);
+                await _localStorage.SetAsync(RememberUsernameKey, false);
+            }
             await _localStorage.SetAsync(RoleKey, role);
 
             var identity = new ClaimsIdentity(new[]
@@ -75,8 +90,12 @@ namespace QuantEngine.Web.Client.Infrastructure
         public async Task MarkUserAsLoggedOutAsync()
         {
             await _localStorage.DeleteAsync(TokenKey);
-            await _localStorage.DeleteAsync(UsernameKey);
             await _localStorage.DeleteAsync(RoleKey);
+            var rememberUsername = await _localStorage.GetAsync<bool>(RememberUsernameKey);
+            if (!rememberUsername)
+            {
+                await _localStorage.DeleteAsync(UsernameKey);
+            }
             NotifyAuthenticationStateChanged(Task.FromResult(new AuthenticationState(_anonymous)));
         }
 
@@ -99,5 +118,16 @@ namespace QuantEngine.Web.Client.Infrastructure
 
             await MarkUserAsLoggedOutAsync();
         }
+
+        public async Task<string?> GetRememberedUsernameAsync()
+        {
+            var rememberUsername = await _localStorage.GetAsync<bool>(RememberUsernameKey);
+            if (!rememberUsername)
+            {
+                return null;
+            }
+
+            return await _localStorage.GetAsync<string>(UsernameKey);
+        }
     }
 }

src/dotnet/QuantEngine.Web/Client/Pages/Login.razor

@@ -18,6 +18,7 @@
         <MudStack Spacing="2">
             <MudTextField Label="관리자 아이디" @bind-Value="Username" Variant="Variant.Outlined" Immediate="true" AutoFocus="true" />
             <MudTextField Label="비밀번호" @bind-Value="Password" Variant="Variant.Outlined" InputType="InputType.Password" Immediate="true" />
+            <MudCheckBox T="bool" @bind-Checked="RememberUsername" Color="Color.Primary" Label="아이디 저장" />
 
             @if (!string.IsNullOrEmpty(ErrorMessage))
             {
@@ -57,6 +58,18 @@
     private string Password { get; set; } = string.Empty;
     private string ErrorMessage { get; set; } = string.Empty;
     private bool IsSubmitting { get; set; } = false;
+    private bool RememberUsername { get; set; } = true;
+
+    protected override async Task OnInitializedAsync()
+    {
+        var customProvider = (CustomAuthenticationStateProvider)AuthStateProvider;
+        var remembered = await customProvider.GetRememberedUsernameAsync();
+        if (!string.IsNullOrWhiteSpace(remembered))
+        {
+            Username = remembered;
+            RememberUsername = true;
+        }
+    }
 
     private sealed class LoginResponse
     {
@@ -91,7 +104,7 @@
                 }
 
                 var customProvider = (CustomAuthenticationStateProvider)AuthStateProvider;
-                await customProvider.MarkUserAsAuthenticatedAsync(auth.Username ?? Username, auth.AccessToken, auth.Role ?? "Admin");
+                await customProvider.MarkUserAsAuthenticatedAsync(auth.Username ?? Username, auth.AccessToken, auth.Role ?? "Admin", RememberUsername);
                 NavigationManager.NavigateTo("/dashboard");
             }
             else