M5: Windows client moderation UI; add C ABI getters for account list, user mute/deafen, channel topic

clients/windows/VoiceCat.App/Forms/BanUserDialog.cs

@@ -0,0 +1,94 @@
+namespace VoiceCat.App.Forms;
+
+/// <summary>
+/// Prompt for a ban reason and duration.
+/// </summary>
+public sealed class BanUserDialog : Form
+{
+    private readonly TextBox _txtReason;
+    private readonly ComboBox _cboDuration;
+
+    public string Reason => _txtReason.Text.Trim();
+    public ulong ExpiresUnixMs { get; private set; }
+
+    public BanUserDialog(string nickname)
+    {
+        Text = $"Ban {nickname}";
+        FormBorderStyle = FormBorderStyle.FixedDialog;
+        MaximizeBox = false;
+        MinimizeBox = false;
+        StartPosition = FormStartPosition.CenterParent;
+        AutoScaleMode = AutoScaleMode.Font;
+        ClientSize = new Size(384, 160);
+
+        var lblReason = new Label
+        {
+            Text = "&Reason:",
+            Location = new Point(12, 12),
+            AutoSize = true,
+        };
+        _txtReason = new TextBox
+        {
+            Location = new Point(12, 34),
+            Size = new Size(360, 23),
+            TabIndex = 1,
+        };
+
+        var lblDuration = new Label
+        {
+            Text = "&Duration:",
+            Location = new Point(12, 66),
+            AutoSize = true,
+        };
+        _cboDuration = new ComboBox
+        {
+            Location = new Point(12, 88),
+            Size = new Size(200, 23),
+            DropDownStyle = ComboBoxStyle.DropDownList,
+            TabIndex = 2,
+        };
+        _cboDuration.Items.AddRange(new object[]
+        {
+            new DurationItem("1 hour", TimeSpan.FromHours(1)),
+            new DurationItem("1 day", TimeSpan.FromDays(1)),
+            new DurationItem("1 week", TimeSpan.FromDays(7)),
+            new DurationItem("Permanent", TimeSpan.Zero),
+        });
+        _cboDuration.SelectedIndex = 1;
+
+        var btnOk = new Button
+        {
+            Text = "&Ban",
+            DialogResult = DialogResult.OK,
+            Location = new Point(216, 126),
+            Size = new Size(75, 27),
+            TabIndex = 3,
+        };
+        var btnCancel = new Button
+        {
+            Text = "&Cancel",
+            DialogResult = DialogResult.Cancel,
+            Location = new Point(297, 126),
+            Size = new Size(75, 27),
+            TabIndex = 4,
+        };
+
+        AcceptButton = btnOk;
+        CancelButton = btnCancel;
+        Controls.AddRange([lblReason, _txtReason, lblDuration, _cboDuration, btnOk, btnCancel]);
+
+        btnOk.Click += (_, _) =>
+        {
+            var selected = _cboDuration.SelectedItem as DurationItem;
+            ExpiresUnixMs = selected?.Duration == TimeSpan.Zero
+                ? 0
+                : (ulong)DateTimeOffset.UtcNow.Add(selected!.Duration).ToUnixTimeMilliseconds();
+        };
+    }
+
+    private sealed class DurationItem(string label, TimeSpan duration)
+    {
+        public TimeSpan Duration { get; } = duration;
+        public override string ToString() => label;
+    }
+}