refactor: Optimize sidebar data loading, update font to ExtraBold, and adjust blur effects for category cards and header.

hdyc-svelte/src/lib/components/Sidebar.svelte

@@ -2,7 +2,18 @@
   import { browser } from '$app/environment';
   import { onMount } from 'svelte';
   import { page } from '$app/stores';
-  import { categories, getCalculatorsByCategory, type CalculatorDef } from '$lib/data/calculators';
+  import { categories } from '$lib/data/stats';
+  import type { CalculatorDef } from '$lib/data/calculators';
+
+  let allCalculators: CalculatorDef[] = [];
+  let isLoaded = false;
+
+  async function loadData() {
+    if (isLoaded || !browser) return;
+    const module = await import('$lib/data/calculators');
+    allCalculators = module.calculators;
+    isLoaded = true;
+  }
 
   let expandedCategory = '';
   let expandedUnits: Record<string, string> = {};
@@ -76,7 +87,12 @@
 
   $: categoryUnitGroups = Object.entries(categories).map(([key, meta]) => {
     const buckets = new Map<string, UnitBucket>();
-    const calcs = getCalculatorsByCategory(key);
+    
+    if (!isLoaded) {
+      return { key, meta, units: [] };
+    }
+
+    const calcs = allCalculators.filter(c => c.category === key && !c.hidden);
     const canonicalByPair = new Map<string, CalculatorDef>();
 
     calcs.forEach(calc => {
@@ -161,6 +177,11 @@
   }
 
   export let open = false;
+
+  $: if (browser && (isDesktop || open)) {
+    loadData();
+  }
+
   $: isSidebarHidden = !isDesktop && !open;
 
   function closeSidebar() {