Fix withRetry to actually catch async rejections

`return fn()` inside an async try block returns the promise directly
without awaiting — rejected promises bypass the catch block entirely.
Changed to `return await fn()` so async failures are caught and retried.

Without this fix, withRetry never retried async callbacks (including
downloadWithProgress and Netlify file uploads).

Author: cderv

src/core/retry.ts

@@ -26,7 +26,7 @@ export async function withRetry<T = void>(
   let attempt = 0;
   while (true) {
     try {
-      return fn();
+      return await fn();
     } catch (err) {
       if (!(err instanceof Error)) throw err;
       if ((attempt++ >= attempts) || (retry && !retry(err))) {