feat: add ActivityLogForm with color-coded DataGridView

src/SpamGuard/Tray/ActivityLogForm.cs

@@ -0,0 +1,95 @@
+namespace SpamGuard.Tray;
+
+using SpamGuard.Models;
+using SpamGuard.Services;
+
+public sealed class ActivityLogForm : Form
+{
+    private readonly ActivityLog _activityLog;
+    private readonly DataGridView _grid;
+
+    public ActivityLogForm(ActivityLog activityLog)
+    {
+        _activityLog = activityLog;
+
+        Text = "SpamGuard - Activity Log";
+        Size = new System.Drawing.Size(800, 500);
+        StartPosition = FormStartPosition.CenterScreen;
+        Icon = IconGenerator.Green;
+
+        _grid = new DataGridView
+        {
+            Dock = DockStyle.Fill,
+            ReadOnly = true,
+            AllowUserToAddRows = false,
+            AllowUserToDeleteRows = false,
+            AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.Fill,
+            SelectionMode = DataGridViewSelectionMode.FullRowSelect,
+            BackgroundColor = System.Drawing.SystemColors.Window,
+            BorderStyle = BorderStyle.None
+        };
+
+        _grid.Columns.Add("Time", "Time");
+        _grid.Columns.Add("From", "From");
+        _grid.Columns.Add("Subject", "Subject");
+        _grid.Columns.Add("Verdict", "Verdict");
+        _grid.Columns.Add("Confidence", "Confidence");
+        _grid.Columns.Add("Reason", "Reason");
+
+        _grid.Columns["Time"]!.Width = 70;
+        _grid.Columns["From"]!.Width = 150;
+        _grid.Columns["Verdict"]!.Width = 80;
+        _grid.Columns["Confidence"]!.Width = 80;
+
+        Controls.Add(_grid);
+
+        RefreshData();
+    }
+
+    public void RefreshData()
+    {
+        if (InvokeRequired)
+        {
+            Invoke(RefreshData);
+            return;
+        }
+
+        var entries = _activityLog.GetRecent(200);
+        _grid.Rows.Clear();
+
+        foreach (var entry in entries)
+        {
+            var rowIndex = _grid.Rows.Add(
+                entry.Timestamp.ToLocalTime().ToString("HH:mm:ss"),
+                entry.Sender,
+                entry.Subject,
+                entry.Verdict.ToString(),
+                entry.Confidence?.ToString("P0") ?? "--",
+                entry.Reason ?? ""
+            );
+
+            var row = _grid.Rows[rowIndex];
+            row.DefaultCellStyle.ForeColor = entry.Verdict switch
+            {
+                Verdict.Spam => System.Drawing.Color.Red,
+                Verdict.Trusted => System.Drawing.Color.Green,
+                Verdict.Uncertain => System.Drawing.Color.Orange,
+                Verdict.Error => System.Drawing.Color.Gray,
+                _ => System.Drawing.SystemColors.ControlText
+            };
+        }
+    }
+
+    protected override void OnFormClosing(FormClosingEventArgs e)
+    {
+        if (e.CloseReason == CloseReason.UserClosing)
+        {
+            e.Cancel = true;
+            Hide();
+        }
+        else
+        {
+            base.OnFormClosing(e);
+        }
+    }
+}