feat(G6): add pending memberships tab to Admin Users

- Add tabs: "Alle Benutzer" + "Ausstehende Anträge"
- Show pending membership requests with approve/reject buttons
- Add RejectMembershipDialog with optional rejection reason

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/Koogle.Web/Components/Pages/Admin/RejectMembershipDialog.razor

@@ -0,0 +1,29 @@
+@using Koogle.Application.DTOs
+
+<MudDialog>
+    <DialogContent>
+        <MudText Class="mb-3">
+            Mitgliedschaftsantrag von <strong>@Pending.DisplayName</strong> für Club <strong>@Pending.ClubName</strong> ablehnen?
+        </MudText>
+        <MudTextField @bind-Value="_reason"
+            Label="Begründung (optional)"
+            Variant="Variant.Outlined"
+            Lines="3"
+            Placeholder="z.B. Kein Platz im Club verfügbar..." />
+    </DialogContent>
+    <DialogActions>
+        <MudButton OnClick="Cancel">Abbrechen</MudButton>
+        <MudButton Color="Color.Error" Variant="Variant.Filled" OnClick="Submit">Ablehnen</MudButton>
+    </DialogActions>
+</MudDialog>
+
+@code {
+    [CascadingParameter] private IMudDialogInstance MudDialog { get; set; } = null!;
+
+    [Parameter] public PendingMembershipDto Pending { get; set; } = null!;
+
+    private string _reason = "";
+
+    private void Cancel() => MudDialog.Cancel();
+    private void Submit() => MudDialog.Close(DialogResult.Ok(_reason));
+}

src/Koogle.Web/Components/Pages/Admin/Users.razor

@@ -15,73 +15,123 @@
 
 <MudText Typo="Typo.h4" Class="mb-4">Benutzer verwalten</MudText>
 
-@if (_isLoading)
-{
-    <MudProgressCircular Indeterminate="true" />
-}
-else
-{
-    <MudTable Items="_users" Dense="true" Hover="true" Filter="FilterFunc" Loading="_isLoading">
-        <ToolBarContent>
-            <MudTextField @bind-Value="_searchString"
-                Placeholder="Suchen..."
-                Adornment="Adornment.Start"
-                AdornmentIcon="@Icons.Material.Filled.Search"
-                IconSize="Size.Medium"
-                Class="mt-0" />
-        </ToolBarContent>
-        <HeaderContent>
-            <MudTh>Name</MudTh>
-            <MudTh>E-Mail</MudTh>
-            <MudTh>Clubs</MudTh>
-            <MudTh>Aktionen</MudTh>
-        </HeaderContent>
-        <RowTemplate>
-            <MudTd DataLabel="Name">@context.DisplayName</MudTd>
-            <MudTd DataLabel="E-Mail">@context.Identity.Email</MudTd>
-            <MudTd DataLabel="Clubs">
-                @if (context.ClubMemberships.Count == 0)
-                {
-                    <MudText Typo="Typo.caption" Color="Color.Warning">Kein Club</MudText>
-                }
-                else
-                {
-                    @foreach (var membership in context.ClubMemberships)
-                    {
-                        <MudChip T="string" Size="Size.Small" Color="@(membership.IsDefault ? Color.Primary : Color.Default)" Class="mr-1 mb-1">
-                            @membership.ClubName
-                            @if (membership.Roles.Any())
+<MudTabs @bind-ActivePanelIndex="_activeTabIndex" Elevation="0" Rounded="true" ApplyEffectsToContainer="true" Class="mb-4">
+    <MudTabPanel Text="Alle Benutzer" BadgeData="@(_users.Count)" BadgeColor="Color.Primary">
+        @if (_isLoading)
+        {
+            <MudProgressCircular Indeterminate="true" />
+        }
+        else
+        {
+            <MudTable Items="_users" Dense="true" Hover="true" Filter="FilterFunc" Loading="_isLoading">
+                <ToolBarContent>
+                    <MudTextField @bind-Value="_searchString"
+                        Placeholder="Suchen..."
+                        Adornment="Adornment.Start"
+                        AdornmentIcon="@Icons.Material.Filled.Search"
+                        IconSize="Size.Medium"
+                        Class="mt-0" />
+                </ToolBarContent>
+                <HeaderContent>
+                    <MudTh>Name</MudTh>
+                    <MudTh>E-Mail</MudTh>
+                    <MudTh>Clubs</MudTh>
+                    <MudTh>Aktionen</MudTh>
+                </HeaderContent>
+                <RowTemplate>
+                    <MudTd DataLabel="Name">@context.DisplayName</MudTd>
+                    <MudTd DataLabel="E-Mail">@context.Identity.Email</MudTd>
+                    <MudTd DataLabel="Clubs">
+                        @if (context.ClubMemberships.Count == 0)
+                        {
+                            <MudText Typo="Typo.caption" Color="Color.Warning">Kein Club</MudText>
+                        }
+                        else
+                        {
+                            @foreach (var membership in context.ClubMemberships)
                             {
-                                <span class="ml-1">(@string.Join(", ", membership.Roles))</span>
+                                <MudChip T="string" Size="Size.Small" Color="@(membership.IsDefault ? Color.Primary : Color.Default)" Class="mr-1 mb-1">
+                                    @membership.ClubName
+                                    @if (membership.Roles.Any())
+                                    {
+                                        <span class="ml-1">(@string.Join(", ", membership.Roles))</span>
+                                    }
+                                </MudChip>
                             }
-                        </MudChip>
-                    }
-                }
-            </MudTd>
-            <MudTd DataLabel="Aktionen">
-                <MudTooltip Text="Club zuweisen">
-                    <MudIconButton Icon="@Icons.Material.Filled.GroupAdd"
-                                   Size="Size.Small"
-                                   OnClick="@(() => OpenAssignClubDialog(context))"/>
-                </MudTooltip>
-                <MudTooltip Text="Rollen verwalten">
-                <MudIconButton Icon="@Icons.Material.Filled.Security"
-                               Size="Size.Small"
-                               OnClick="@(() => OpenManageRolesDialog(context))"/>
-                </MudTooltip>
-            </MudTd>
-        </RowTemplate>
-        <PagerContent>
-            <MudTablePager />
-        </PagerContent>
-    </MudTable>
-}
+                        }
+                    </MudTd>
+                    <MudTd DataLabel="Aktionen">
+                        <MudTooltip Text="Club zuweisen">
+                            <MudIconButton Icon="@Icons.Material.Filled.GroupAdd"
+                                           Size="Size.Small"
+                                           OnClick="@(() => OpenAssignClubDialog(context))"/>
+                        </MudTooltip>
+                        <MudTooltip Text="Rollen verwalten">
+                        <MudIconButton Icon="@Icons.Material.Filled.Security"
+                                       Size="Size.Small"
+                                       OnClick="@(() => OpenManageRolesDialog(context))"/>
+                        </MudTooltip>
+                    </MudTd>
+                </RowTemplate>
+                <PagerContent>
+                    <MudTablePager />
+                </PagerContent>
+            </MudTable>
+        }
+    </MudTabPanel>
+
+    <MudTabPanel Text="Ausstehende Anträge" BadgeData="@(_pendingMemberships.Count)" BadgeColor="@(_pendingMemberships.Any() ? Color.Warning : Color.Default)">
+        @if (_isLoadingPending)
+        {
+            <MudProgressCircular Indeterminate="true" />
+        }
+        else if (!_pendingMemberships.Any())
+        {
+            <MudAlert Severity="Severity.Info" Class="mt-4">Keine ausstehenden Mitgliedschaftsanträge.</MudAlert>
+        }
+        else
+        {
+            <MudTable Items="_pendingMemberships" Dense="true" Hover="true" Class="mt-2">
+                <HeaderContent>
+                    <MudTh>Name</MudTh>
+                    <MudTh>E-Mail</MudTh>
+                    <MudTh>Club</MudTh>
+                    <MudTh>Angefragt am</MudTh>
+                    <MudTh>Aktionen</MudTh>
+                </HeaderContent>
+                <RowTemplate>
+                    <MudTd DataLabel="Name">@context.DisplayName</MudTd>
+                    <MudTd DataLabel="E-Mail">@context.Email</MudTd>
+                    <MudTd DataLabel="Club">@context.ClubName</MudTd>
+                    <MudTd DataLabel="Angefragt am">@context.RequestedAt.ToString("dd.MM.yyyy HH:mm")</MudTd>
+                    <MudTd DataLabel="Aktionen">
+                        <MudTooltip Text="Genehmigen">
+                            <MudIconButton Icon="@Icons.Material.Filled.Check"
+                                           Color="Color.Success"
+                                           Size="Size.Small"
+                                           OnClick="@(() => ApproveMembership(context))"/>
+                        </MudTooltip>
+                        <MudTooltip Text="Ablehnen">
+                            <MudIconButton Icon="@Icons.Material.Filled.Close"
+                                           Color="Color.Error"
+                                           Size="Size.Small"
+                                           OnClick="@(() => OpenRejectDialog(context))"/>
+                        </MudTooltip>
+                    </MudTd>
+                </RowTemplate>
+            </MudTable>
+        }
+    </MudTabPanel>
+</MudTabs>
 
 @code {
     private List<UserDto> _users = new();
     private List<ClubDto> _clubs = new();
+    private List<PendingMembershipDto> _pendingMemberships = new();
     private bool _isLoading = true;
+    private bool _isLoadingPending = true;
     private string _searchString = "";
+    private int _activeTabIndex = 0;
 
     protected override async Task OnInitializedAsync()
     {
@@ -91,6 +141,7 @@ else
     private async Task LoadData()
     {
         _isLoading = true;
+        _isLoadingPending = true;
         try
         {
             var usersTask = UserService.GetAllUsersAsync();
@@ -99,10 +150,33 @@ else
 
             _users = (await usersTask).ToList();
             _clubs = await clubsTask;
+            _isLoading = false;
+
+            await LoadPendingMemberships();
         }
         finally
         {
             _isLoading = false;
+            _isLoadingPending = false;
+        }
+    }
+
+    private async Task LoadPendingMemberships()
+    {
+        _isLoadingPending = true;
+        try
+        {
+            var allPending = new List<PendingMembershipDto>();
+            foreach (var club in _clubs)
+            {
+                var clubPending = await UserService.GetPendingMembershipsAsync(club.Id);
+                allPending.AddRange(clubPending);
+            }
+            _pendingMemberships = allPending.OrderByDescending(p => p.RequestedAt).ToList();
+        }
+        finally
+        {
+            _isLoadingPending = false;
         }
     }
 
@@ -174,4 +248,58 @@ else
             await LoadData();
         }
     }
+
+    private async Task ApproveMembership(PendingMembershipDto pending)
+    {
+        var currentUser = await UserService.GetCurrentUserAsync();
+        if (currentUser == null)
+        {
+            Snackbar.Add("Nicht angemeldet", Severity.Error);
+            return;
+        }
+
+        var success = await UserService.ApproveMembershipAsync(pending.UserProfileId, pending.ClubId, currentUser.ProfileId);
+        if (success)
+        {
+            Snackbar.Add($"Mitgliedschaft von {pending.DisplayName} genehmigt", Severity.Success);
+            await LoadData();
+        }
+        else
+        {
+            Snackbar.Add("Fehler beim Genehmigen der Mitgliedschaft", Severity.Error);
+        }
+    }
+
+    private async Task OpenRejectDialog(PendingMembershipDto pending)
+    {
+        var parameters = new DialogParameters
+        {
+            { "Pending", pending }
+        };
+
+        var options = new DialogOptions { CloseButton = true, MaxWidth = MaxWidth.Small };
+        var dialog = await DialogService.ShowAsync<RejectMembershipDialog>("Mitgliedschaft ablehnen", parameters, options);
+        var result = await dialog.Result;
+
+        if (result != null && !result.Canceled && result.Data is string reason)
+        {
+            var currentUser = await UserService.GetCurrentUserAsync();
+            if (currentUser == null)
+            {
+                Snackbar.Add("Nicht angemeldet", Severity.Error);
+                return;
+            }
+
+            var success = await UserService.RejectMembershipAsync(pending.UserProfileId, pending.ClubId, currentUser.ProfileId, reason);
+            if (success)
+            {
+                Snackbar.Add($"Mitgliedschaft von {pending.DisplayName} abgelehnt", Severity.Success);
+                await LoadData();
+            }
+            else
+            {
+                Snackbar.Add("Fehler beim Ablehnen der Mitgliedschaft", Severity.Error);
+            }
+        }
+    }
 }