Fix categories

hdyc-svelte/src/routes/+page.svelte

@@ -3,12 +3,22 @@
   import CategoryCard from '$lib/components/CategoryCard.svelte';
   import SearchBar from '$lib/components/SearchBar.svelte';
 
-  const cats = Object.entries(categories).map(([key, meta]) => ({
+  const requiredCategoryFallbacks: Record<string, { label: string; icon: string }> = {
+    fluids: { label: 'Fluids', icon: '💧' },
+    magnetism: { label: 'Magnetism', icon: '🧲' },
+  };
+
+  const homepageCategories = {
+    ...requiredCategoryFallbacks,
+    ...categories,
+  };
+
+  const cats = Object.entries(homepageCategories).map(([key, meta]) => ({
     key,
     ...meta,
   }));
   const totalCalculators = calculators.length;
-  const totalCategories = Object.keys(categories).length;
+  const totalCategories = Object.keys(homepageCategories).length;
 </script>
 
 <svelte:head>