fix: 分享卡片关闭按钮定位到卡片右上角

src/components/ShareCardModal.tsx

@@ -878,16 +878,14 @@ export default function ShareCardModal({
             exit={{ opacity: 0, scale: 0.92 }}
             transition={{ duration: 0.25, ease: "easeOut" }}
           >
-            {/* Close button (floating) */}
-            <button
-              onClick={onClose}
-              className="mb-3 flex h-9 w-9 shrink-0 items-center justify-center self-end rounded-full bg-white/10 text-gray-300 transition-colors active:bg-white/20"
-            >
-              <X size={18} />
-            </button>
-
-            {/* Card */}
-            <div className="flex shrink-0 justify-center">
+            {/* Card + close button wrapper */}
+            <div className="relative flex shrink-0 justify-center">
+              <button
+                onClick={onClose}
+                className="absolute right-3 top-3 z-10 flex h-8 w-8 items-center justify-center rounded-full bg-black/40 text-white/70 transition-colors active:bg-black/60"
+              >
+                <X size={16} />
+              </button>
               {imageLoading ? (
                 <div
                   style={{ width: 340, height: 400 }}