feat(ui): add dark mode support to Toast component

Add dark: variants to all toast type colors and use semantic theme
tokens (text-foreground, text-muted-foreground) for text elements.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/renderer/src/components/ui/Toast.tsx

@@ -19,24 +19,24 @@ interface ToastItemProps {
 
 const typeStyles: Record<ToastType, { bg: string; border: string; icon: string }> = {
   success: {
-    bg: 'bg-green-50',
-    border: 'border-green-200',
-    icon: 'text-green-500'
+    bg: 'bg-green-50 dark:bg-green-950',
+    border: 'border-green-200 dark:border-green-800',
+    icon: 'text-green-500 dark:text-green-400'
   },
   error: {
-    bg: 'bg-red-50',
-    border: 'border-red-200',
-    icon: 'text-red-500'
+    bg: 'bg-red-50 dark:bg-red-950',
+    border: 'border-red-200 dark:border-red-800',
+    icon: 'text-red-500 dark:text-red-400'
   },
   warning: {
-    bg: 'bg-yellow-50',
-    border: 'border-yellow-200',
-    icon: 'text-yellow-500'
+    bg: 'bg-yellow-50 dark:bg-yellow-950',
+    border: 'border-yellow-200 dark:border-yellow-800',
+    icon: 'text-yellow-500 dark:text-yellow-400'
   },
   info: {
-    bg: 'bg-blue-50',
-    border: 'border-blue-200',
-    icon: 'text-blue-500'
+    bg: 'bg-blue-50 dark:bg-blue-950',
+    border: 'border-blue-200 dark:border-blue-800',
+    icon: 'text-blue-500 dark:text-blue-400'
   }
 }
 
@@ -55,10 +55,10 @@ function ToastItem({ id, type, message, onClose }: ToastItemProps) {
       className={`flex items-center gap-3 px-4 py-3 rounded-lg border ${styles.bg} ${styles.border} shadow-lg min-w-72`}
     >
       <span className={styles.icon}>{ToastIcon[type]}</span>
-      <p className="flex-1 text-sm text-gray-800">{message}</p>
+      <p className="flex-1 text-sm text-foreground">{message}</p>
       <button
         onClick={() => onClose(id)}
-        className="p-1 text-gray-400 hover:text-gray-600 focus:outline-none"
+        className="p-1 text-muted-foreground hover:text-foreground focus:outline-none"
       >
         <X className="w-4 h-4" />
       </button>