fix: handle 404 for scenes endpoint gracefully

- Scenes endpoint may not be implemented in Core API yet
- useVLMScenes returns empty array instead of error on 404

src/composables/useVLM.ts

@@ -61,6 +61,11 @@ export function useVLMScenes(fileUuid: string) {
     try {
       const base = getApiBase()
       const resp = await fetch(`${base}/api/v1/file/${fileUuid}/scenes`)
+      if (resp.status === 404) {
+        // Scenes endpoint may not be implemented yet
+        scenes.value = []
+        return
+      }
       if (!resp.ok) throw new Error(`HTTP ${resp.status}`)
       const data = await resp.json()
       scenes.value = Array.isArray(data) ? data : (data.scenes || [])