style: 移除确认对话框的圆角以匹配整体无圆角设计

src/lib/components/ConfirmDialog.svelte

@@ -68,7 +68,7 @@
 		background: var(--bg-color, #ffffff);
 		color: var(--text-color, #000000);
 		border: 2px solid var(--text-color, #000000);
-		border-radius: 8px;
+		border-radius: 0;
 		width: 90%;
 		max-width: 400px;
 		box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
@@ -100,7 +100,7 @@
 		padding: 8px 16px;
 		font-size: 0.9rem;
 		font-weight: 600;
-		border-radius: 4px;
+		border-radius: 0;
 		cursor: pointer;
 		font-family: inherit;
 		transition: all 0.2s;