refactor(frontend): polish ExportDataModal (derived selection, safe URL revoke, error escape)

frontend/src/components/ExportDataModal.jsx

@@ -15,7 +15,7 @@ function triggerDownload(filename, text) {
   document.body.appendChild(a);
   a.click();
   document.body.removeChild(a);
-  URL.revokeObjectURL(url);
+  setTimeout(() => URL.revokeObjectURL(url), 0);
 }
 
 export default function ExportDataModal({ experimentTitle, experimentId, dailyTemplate, animals, onClose }) {
@@ -37,12 +37,9 @@ export default function ExportDataModal({ experimentTitle, experimentId, dailyTe
 
   const params = useMemo(() => listExportableParams(dailyTemplate, statuses), [dailyTemplate, statuses]);
 
-  // Default the selection to the first parameter once params are available.
-  useEffect(() => {
-    if (selectedId === null && params.length > 0) setSelectedId(params[0].id);
-  }, [params, selectedId]);
-
-  const selectedParam = params.find((p) => p.id === selectedId) ?? null;
+  // Derive the effective selection: the user's pick, else the first parameter.
+  const effectiveId = selectedId ?? params[0]?.id ?? null;
+  const selectedParam = params.find((p) => p.id === effectiveId) ?? null;
 
   const matrix = useMemo(
     () => (selectedParam ? buildMatrix(statuses, animals, selectedParam) : { columns: [], rows: [] }),
@@ -69,7 +66,14 @@ export default function ExportDataModal({ experimentTitle, experimentId, dailyTe
   }
 
   if (loading) return <p className="text-sm text-gray-400" aria-live="polite">Loading data…</p>;
-  if (error) return <Alert type="error" message={error} />;
+  if (error) return (
+    <div className="space-y-4">
+      <Alert type="error" message={error} />
+      <div className="flex justify-end">
+        <Button variant="secondary" onClick={onClose}>Close</Button>
+      </div>
+    </div>
+  );
 
   return (
     <div className="space-y-4">
@@ -81,7 +85,7 @@ export default function ExportDataModal({ experimentTitle, experimentId, dailyTe
         <label htmlFor="export-param" className="block text-xs font-medium text-gray-500 mb-1">Parameter</label>
         <select
           id="export-param"
-          value={selectedId ?? ''}
+          value={effectiveId ?? ''}
           onChange={(e) => setSelectedId(e.target.value)}
           className="w-full border border-gray-200 rounded px-2 py-1.5 text-sm bg-white focus:outline-none focus:ring-1 focus:ring-indigo-400"
         >