Refactor utility functions and IndexedDB handling

Extracted and centralized common utility functions such as createCanvas, normalizeToUint8, and generateUniqueFileName in CommonUtils.js to reduce code duplication. Added createImageFromSource to ImageUtils.js. Refactored db.js to use a helper for IndexedDB requests, simplifying error handling and reducing boilerplate. Updated CanvasIO.js, CanvasLayers.js, and Canvas_view.js to use the new utilities.

js/ImageUtils.js

@@ -356,6 +356,20 @@ export function getImageInfo(image) {
     };
 }
 
+/**
+ * Tworzy obraz z podanego źródła - eliminuje duplikaty w kodzie
+ * @param {string} source - Źródło obrazu (URL, data URL, etc.)
+ * @returns {Promise<HTMLImageElement>} Promise z obrazem
+ */
+export function createImageFromSource(source) {
+    return new Promise((resolve, reject) => {
+        const img = new Image();
+        img.onload = () => resolve(img);
+        img.onerror = reject;
+        img.src = source;
+    });
+}
+
 /**
  * Tworzy pusty obraz o podanych wymiarach
  * @param {number} width - Szerokość