Add port config, quick-switch toolbar, and dark mode styling

- Add Config button to each monitor for hiding ports, custom labels, and quick-switch selection
- Add quick-switch toolbar at top of popup for one-click input switching
- Add dark mode styling for all controls (buttons, combobox, dropdown items)
- Add loading spinner animation
- Add Exit button in header
- Fix dropdown selection to correctly show current input

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

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

Library/ViewModel/MonitorConfig.cs

@@ -0,0 +1,44 @@
+namespace CMM.Library.ViewModel;
+
+/// <summary>
+/// Configuration for a single monitor's ports
+/// </summary>
+public class MonitorConfig
+{
+    public string SerialNumber { get; set; } = string.Empty;
+    public string MonitorName { get; set; } = string.Empty;
+    public List<PortConfig> Ports { get; set; } = new();
+}
+
+/// <summary>
+/// Configuration for a single input port
+/// </summary>
+public class PortConfig
+{
+    public int VcpValue { get; set; }
+    public string DefaultName { get; set; } = string.Empty;
+    public string CustomLabel { get; set; } = string.Empty;
+    public bool IsHidden { get; set; }
+    public bool ShowInQuickSwitch { get; set; }
+
+    public string DisplayName => string.IsNullOrWhiteSpace(CustomLabel) ? DefaultName : CustomLabel;
+}
+
+/// <summary>
+/// Quick switch item shown in toolbar
+/// </summary>
+public class QuickSwitchItem
+{
+    public string MonitorSerialNumber { get; set; } = string.Empty;
+    public string MonitorName { get; set; } = string.Empty;
+    public int PortVcpValue { get; set; }
+    public string PortLabel { get; set; } = string.Empty;
+}
+
+/// <summary>
+/// Root configuration object
+/// </summary>
+public class AppConfig
+{
+    public List<MonitorConfig> Monitors { get; set; } = new();
+}