feat(files): add file management UI for scenarios and runs

- add scenario upload and download UI with typed file API helpers
- show run artifacts on run detail pages after polling completes
- handle multipart uploads and absolute file paths for downloads

client/src/pages/scenario/CreateScenarioPage.tsx

@@ -22,7 +22,10 @@ export function CreateScenarioPage() {
   const [saving, setSaving] = useState(false);
 
   useEffect(() => {
-    environments.list(1, 200).then((r) => setEnvs(r?.data ?? [])).catch(() => {});
+    environments
+      .list(1, 200)
+      .then((r) => setEnvs(r?.data ?? []))
+      .catch(() => {});
   }, []);
 
   const handleSubmit = async (e: SubmitEvent<HTMLFormElement>) => {
@@ -33,7 +36,11 @@ export function CreateScenarioPage() {
     }
     setSaving(true);
     try {
-      const scenario = await scenarios.create(name.trim(), description.trim() || undefined, environmentId || undefined);
+      const scenario = await scenarios.create(
+        name.trim(),
+        description.trim() || undefined,
+        environmentId || undefined,
+      );
       toast.success(t('scenarios.created'));
       navigate(`/scenarios/${scenario.id}`);
     } catch (err) {