feat(frontend): thread file size from upload through to the download card

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/pages/HomePage.jsx

@@ -80,7 +80,8 @@ export function HomePage() {
   async function handleConvert() {
     const validItems = pendingFiles.filter((item) => item.targetFormat);
     const jobs = await uploadFiles(validItems);
-    setSubmittedJobs((current) => [...current, ...jobs]);
+    const jobsWithSize = jobs.map((job, i) => ({ ...job, size: validItems[i].file.size }));
+    setSubmittedJobs((current) => [...current, ...jobsWithSize]);
     setPendingFiles([]);
   }
 
@@ -116,9 +117,9 @@ export function HomePage() {
         <ul className="job-list">
           {submittedJobs.map((job, index) =>
             job.id ? (
-              <FileCard key={job.id} fileName={job.file} jobId={job.id} />
+              <FileCard key={job.id} fileName={job.file} fileSize={job.size} jobId={job.id} />
             ) : (
-              <FileCard key={`${job.file}-${index}`} fileName={job.file} initialError={job.error} />
+              <FileCard key={`${job.file}-${index}`} fileName={job.file} fileSize={job.size} initialError={job.error} />
             )
           )}
         </ul>