feat(sns-export): split media export selection into image/live/video

src/pages/SnsPage.scss

@@ -1984,10 +1984,31 @@
     font-size: 12px;
     color: var(--text-tertiary);
     margin: 0;
-    padding-left: 24px;
     line-height: 1.4;
 }
 
+.export-media-check-grid {
+    display: grid;
+    grid-template-columns: repeat(auto-fit, minmax(110px, 1fr));
+    gap: 8px;
+
+    label {
+        display: inline-flex;
+        align-items: center;
+        gap: 6px;
+        font-size: 13px;
+        color: var(--text-primary);
+        padding: 8px 10px;
+        border: 1px solid var(--border-color);
+        border-radius: 8px;
+        background: var(--bg-secondary);
+    }
+
+    input[type='checkbox'] {
+        margin: 0;
+    }
+}
+
 .export-progress {
     display: flex;
     flex-direction: column;