Refactor image model selection and dimensions

lib/file-utils.ts

@@ -0,0 +1,29 @@
+export function validateFileForUpload(file: File, rejectWebP: boolean = true): { valid: boolean; error?: string } {
+  // Reject WebP files
+  if (rejectWebP && (file.type === "image/webp" || file.name.toLowerCase().endsWith('.webp'))) {
+    return {
+      valid: false,
+      error: "WebP files not supported. Please upload PNG, JPG, or JPEG files instead of WebP."
+    }
+  }
+
+  // Check if file is an image
+  if (!file.type.startsWith("image/")) {
+    return {
+      valid: false,
+      error: "Only image files are supported."
+    }
+  }
+
+  return { valid: true }
+}
+
+export function generateFilePreview(file: File): Promise<string> {
+  return new Promise((resolve) => {
+    const reader = new FileReader()
+    reader.onload = (e) => {
+      resolve(e.target?.result as string)
+    }
+    reader.readAsDataURL(file)
+  })
+}