Video: async conversion with live progress polling

- /convert now returns immediately, ffmpeg runs in background
- Client polls /progress every second for live progress %
- Progress endpoint returns downloadUrl/outputSize when done
- UI shows real-time percentage during conversion

public/video.html

@@ -939,15 +939,8 @@
                 throw new Error(err.error || 'Ошибка запуска');
             }
 
-            const data = await res.json();
-
-            // Server may return immediately (sync) or poll (async)
-            if (data.status === 'done' || data.downloadUrl) {
-                setProgressUI(100, 'Готово!');
-                onConversionDone(data);
-            } else {
+            // Server starts processing in background, poll for progress
             startPolling();
-            }
         } catch (err) {
             showConversionError(err.message || 'Ошибка конвертации');
         }

routes/video.js

@@ -184,20 +184,21 @@ router.post('/convert', express.json(), async (req, res) => {
 
     args.push(outFile);
 
-    await runFFmpeg(args, jobId);
+    // Start ffmpeg in background — respond immediately
+    res.json({ status: 'processing' });
+
+    runFFmpeg(args, jobId).then(() => {
       job.status = 'done';
       job.progress = 100;
-
       const outStat = fs.statSync(outFile);
-    const savings = job.size > 0 ? Math.round((1 - outStat.size / job.size) * 100) : 0;
-
-    log.info(`Video ${mode}: ${job.originalName} → ${format} (${(outStat.size / 1024 / 1024).toFixed(1)}MB, ${savings}% saved)`);
-
-    res.json({
-      status: 'done',
-      downloadUrl: `/video/download/${jobId}${outExt}`,
-      outputSize: outStat.size,
-      savings,
+      job.outputSize = outStat.size;
+      job.savings = job.size > 0 ? Math.round((1 - outStat.size / job.size) * 100) : 0;
+      job.downloadUrl = `/video/download/${jobId}${outExt}`;
+      log.info(`Video ${mode}: ${job.originalName} → ${format} (${(outStat.size / 1024 / 1024).toFixed(1)}MB, ${job.savings}% saved)`);
+    }).catch(err => {
+      job.status = 'error';
+      job.error = err.message.slice(0, 200);
+      log.error('Video convert error', { error: err.message });
     });
   } catch (err) {
     job.status = 'error';
@@ -206,11 +207,20 @@ router.post('/convert', express.json(), async (req, res) => {
   }
 });
 
-// Progress
+// Progress (returns downloadUrl when done)
 router.get('/progress/:jobId', (req, res) => {
   const job = jobs.get(req.params.jobId);
   if (!job) return res.status(404).json({ error: 'Not found' });
-  res.json({ status: job.status, progress: job.progress });
+  const result = { status: job.status, progress: job.progress };
+  if (job.status === 'done') {
+    result.downloadUrl = job.downloadUrl;
+    result.outputSize = job.outputSize;
+    result.savings = job.savings;
+  }
+  if (job.status === 'error') {
+    result.error = job.error || 'Ошибка обработки';
+  }
+  res.json(result);
 });
 
 // Download result