Add centralized unit definitions

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

@@ -0,0 +1,67 @@
+<script lang="ts">
+  import { getDefinition } from '$lib/data/unitDefinitions';
+  import type { CalculatorDef } from '$lib/data/calculators';
+
+  export let config: CalculatorDef;
+
+  const label1 = config.labels.in1 || 'Unit 1';
+  const label2 = config.labels.in2 || 'Unit 2';
+
+  const def1 = getDefinition(label1);
+  const def2 = getDefinition(label2);
+</script>
+
+<section class="definition-card">
+  <h3>Unit definitions</h3>
+  <div class="definition-grid">
+    <article>
+      <strong>{label1}</strong>
+      <p>{def1 ?? `Definition pending for ${label1}.`}</p>
+    </article>
+    <article>
+      <strong>{label2}</strong>
+      <p>{def2 ?? `Definition pending for ${label2}.`}</p>
+    </article>
+  </div>
+</section>
+
+<style>
+  .definition-card {
+    margin: 0 2rem 2rem;
+    padding: 1.25rem 1.5rem;
+    border-radius: 12px;
+    background: var(--section-bg);
+    border: 1px solid var(--border);
+  }
+
+  .definition-card h3 {
+    margin: 0 0 0.75rem;
+    font-size: 1rem;
+    font-weight: 600;
+  }
+
+  .definition-grid {
+    display: grid;
+    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
+    gap: 1rem;
+  }
+
+  .definition-grid article {
+    background: var(--card-bg);
+    border: 1px solid var(--border);
+    border-radius: 10px;
+    padding: 0.9rem;
+  }
+
+  .definition-grid strong {
+    display: block;
+    font-size: 0.95rem;
+    margin-bottom: 0.4rem;
+  }
+
+  .definition-grid p {
+    margin: 0;
+    font-size: 0.85rem;
+    color: var(--text-muted);
+  }
+</style>