fix(ui): force panel relayout when switching between list/settings

MenuBarExtra(.window) caches the NSPanel size from list mode (~720 with
many stocks) and does not auto-shrink when switching to the 480-tall
settings view, leaving a large blank gap. Adding .id(showSettings) tells
SwiftUI to rebuild the view subtree on mode change, prompting the panel
to recompute its size from the new content.

release: 1.3.3 → 1.3.4

StockMonitor/Views/DropdownView.swift

@@ -105,5 +105,6 @@ struct DropdownView: View {
         .frame(width: 320)
         .fixedSize(horizontal: false, vertical: true)
         .background(Color(nsColor: .windowBackgroundColor))
+        .id(showSettings)
     }
 }