feat: add configurable S3 object storage

src/api/user.rs

@@ -500,7 +500,7 @@ async fn list_history(
         status: String,
         output_format: String,
         error_message: Option<String>,
-        storage_path: Option<String>,
+        has_storage: bool,
     }
 
     let now = Utc::now();
@@ -517,7 +517,7 @@ async fn list_history(
               status::text AS status,
               output_format,
               error_message,
-              storage_path
+              COALESCE(storage_key, storage_path) IS NOT NULL AS has_storage
             FROM task_files
             WHERE task_id = $1
             ORDER BY created_at ASC
@@ -540,7 +540,7 @@ async fn list_history(
                 output_format: file.output_format,
                 error_message: file.error_message,
                 download_url: if file.status == "completed"
-                    && file.storage_path.is_some()
+                    && file.has_storage
                     && task.expires_at > now
                 {
                     Some(format!("/downloads/{}", file.id))