refactor(import): Implement DownloadManager, FolderBrowser, ImageProcessor, and RecipeDataManager for enhanced recipe import functionality

- Added DownloadManager to handle saving recipes and downloading missing LoRAs.
- Introduced FolderBrowser for selecting LoRA root directories and managing folder navigation.
- Created ImageProcessor for handling image uploads and URL inputs for recipe analysis.
- Developed RecipeDataManager to manage recipe details, including metadata and LoRA information.
- Implemented ImportStepManager to control the flow of the import process and manage UI steps.
- Added utility function for formatting file sizes for better user experience.

static/js/utils/formatters.js

@@ -0,0 +1,12 @@
+/**
+ * Format a file size in bytes to a human-readable string
+ * @param {number} bytes - The size in bytes
+ * @returns {string} Formatted size string (e.g., "1.5 MB")
+ */
+export function formatFileSize(bytes) {
+    if (!bytes || isNaN(bytes)) return '';
+    
+    const sizes = ['B', 'KB', 'MB', 'GB'];
+    const i = Math.floor(Math.log(bytes) / Math.log(1024));
+    return (bytes / Math.pow(1024, i)).toFixed(2) + ' ' + sizes[i];
+}