fix: surface first error detail in fix-artist-sort job message for debugging

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/novasonic-server.js

@@ -648,6 +648,7 @@ app.post('/api/fix-artist-sort', async (req, res) => {
     updateJob(jobId, { status: 'running', progress: 10, message: `${songs.length} Songs gefunden…` });
 
     let done = 0, errors = 0;
+    const errorDetails = [];
     const safeArtistDir = sanitize(artistSort.split(/[,;&]/)[0].trim());
 
     for (const ndSong of songs) {
@@ -663,7 +664,12 @@ app.post('/api/fix-artist-sort', async (req, res) => {
             || _findFileRecursive(CONFIG.musicPath, fileName)
             || _findFileByStemOrRomaji(CONFIG.musicPath, titleStem);
           if (found) filePath = found;
-          else { log(jobId, `⚠ Nicht gefunden: ${path.basename(ndSong.path || '')}`); errors++; continue; }
+          else {
+            const detail = `Nicht gefunden: ${path.basename(ndSong.path || '')}`;
+            log(jobId, `⚠ ${detail}`);
+            errorDetails.push(detail);
+            errors++; continue;
+          }
         }
 
         const fileExt = path.extname(filePath);
@@ -710,7 +716,9 @@ app.post('/api/fix-artist-sort', async (req, res) => {
         updateJob(jobId, { progress: 10 + Math.round((done / songs.length) * 80), message: `${done}/${songs.length} Songs aktualisiert…` });
         log(jobId, `✅ ${ndSong.title}`);
       } catch (e) {
-        log(jobId, `❌ ${ndSong.title}: ${e.message}`);
+        const detail = `${ndSong.title}: ${e.message}`;
+        log(jobId, `❌ ${detail}`);
+        errorDetails.push(detail);
         errors++;
       }
     }
@@ -721,7 +729,10 @@ app.post('/api/fix-artist-sort', async (req, res) => {
       await fetch(`${ndUrl}/rest/startScan?u=${encodeURIComponent(user)}&t=${t}&s=${s}&v=1.16.1&c=novasonic&f=json`, { signal: AbortSignal.timeout(5000) });
     } catch {}
 
-    const msg = errors > 0 ? `${done} aktualisiert, ${errors} Fehler` : `${done} Songs aktualisiert`;
+    const firstErr = errorDetails[0] ? ` (${errorDetails[0]})` : '';
+    const msg = errors > 0
+      ? `${done} aktualisiert, ${errors} Fehler${firstErr}`
+      : `${done} Songs aktualisiert`;
     updateJob(jobId, { status: 'done', progress: 100, message: msg });
   })().catch(e => updateJob(jobId, { status: 'error', message: e.message }));
 });