fix image

site/src/components/ActivityDetail.svelte

@@ -70,7 +70,17 @@
     return DOMPurify.sanitize(marked(rawDescription, { renderer }) as string);
   })();
 
-  $: imageBase = `${base}data/activities/images/${activity.id}/`;
+  // Derive image dir from detail_url so multi-user paths resolve correctly.
+  // "dave/_merged/activities/foo.json" → "/data/dave/_merged/activities/images/{id}/"
+  $: imageBase = (() => {
+    const du = activity.detail_url ?? '';
+    const dir = du.startsWith('http')
+      ? du.substring(0, du.lastIndexOf('/') + 1)
+      : du.includes('/')
+        ? `${base}data/${du.substring(0, du.lastIndexOf('/') + 1)}`
+        : `${base}data/activities/`;
+    return `${dir}images/${activity.id}/`;
+  })();
   $: galleryImages = (detail?.custom as any)?.images as string[] ?? [];