refactor: consolidate upload helpers

lib/model-paths.ts

@@ -0,0 +1,7 @@
+export function getModelFolderPath(folderName: string) {
+  return `public/models/${folderName}`
+}
+
+export function getModelAssetPath(folderName: string, filename: string) {
+  return `${getModelFolderPath(folderName)}/${filename}`
+}