Add duplicate detection with fuzzy matching and fix artist metadata extraction

app/admin/page.tsx

@@ -462,6 +462,16 @@ export default function AdminPage() {
                         song: data.song,
                         validation: data.validation
                     });
+                } else if (res.status === 409) {
+                    // Duplicate detected
+                    const data = await res.json();
+                    results.push({
+                        filename: file.name,
+                        success: false,
+                        isDuplicate: true,
+                        duplicate: data.duplicate,
+                        error: `Duplicate: Already exists as "${data.duplicate.title}" by "${data.duplicate.artist}"`
+                    });
                 } else {
                     results.push({
                         filename: file.name,
@@ -486,12 +496,24 @@ export default function AdminPage() {
 
         // Auto-trigger categorization after uploads
         const successCount = results.filter(r => r.success).length;
+        const duplicateCount = results.filter(r => r.isDuplicate).length;
+        const failedCount = results.filter(r => !r.success && !r.isDuplicate).length;
         if (successCount > 0) {
-            setMessage(`✅ Uploaded ${successCount}/${files.length} songs successfully!\n\n🤖 Starting auto-categorization...`);
+            let msg = `✅ Uploaded ${successCount}/${files.length} songs successfully!`;
+            if (duplicateCount > 0) {
+                msg += `\n⚠️ Skipped ${duplicateCount} duplicate(s)`;
+            }
+            if (failedCount > 0) {
+                msg += `\n❌ ${failedCount} failed`;
+            }
+            msg += '\n\n🤖 Starting auto-categorization...';
+            setMessage(msg);
             // Small delay to let user see the message
             setTimeout(() => {
                 handleAICategorization();
             }, 1000);
+        } else if (duplicateCount > 0 && failedCount === 0) {
+            setMessage(`⚠️ All ${duplicateCount} file(s) were duplicates - nothing uploaded.`);
         } else {
             setMessage(`❌ All uploads failed.`);
         }