fix: make thumbnail generation for images in S3 configurable

proto/api/v1/attachment_service.proto

@@ -84,6 +84,9 @@ message Attachment {
   // Optional. The related memo. Refer to `Memo.name`.
   // Format: memos/{memo}
   optional string memo = 8 [(google.api.field_behavior) = OPTIONAL];
+
+  // Optional. Output only. Whether to use thumbnails for this attachment when stored in S3.
+  optional bool use_thumbnail_for_s3_image = 9 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
 
 message CreateAttachmentRequest {

proto/api/v1/workspace_service.proto

@@ -147,6 +147,9 @@ message WorkspaceSetting {
     }
     // The S3 config.
     S3Config s3_config = 4;
+    // use_thumbnails_for_s3_images enables thumbnail generation for images stored in S3.
+    // When false, images stored in S3 will not have thumbnails generated.
+    bool use_thumbnails_for_s3_images = 5;
   }
 
   // Memo-related workspace settings and policies.