feat: Implement ETag-based conditional caching for API and HTML, add immutable caching for images, and introduce concurrency control with resizing for picture syncing.

category-syncer.js

@@ -61,12 +61,11 @@ class CategorySyncer extends EventEmitter {
         try {
             await this._syncFromDb();
             const duration = Date.now() - startTime;
-            console.log(`✅ Sync completed successfully in ${duration}ms.`);
 
-            // Log next sync time
+            // Log completion and next sync time
             const syncInterval = parseInt(process.env.SYNC_INTERVAL_MS) || 60000;
             const minutes = Math.round(syncInterval / 60000);
-            console.log(`⏰ Next sync in ${minutes} minute${minutes !== 1 ? 's' : ''}`);
+            console.log(`✅ Sync completed in ${duration}ms. Next sync in ${minutes} minute${minutes !== 1 ? 's' : ''}`);
         } catch (err) {
             console.error('❌ Sync failed:', err);
         } finally {