feat: add copy PNG to clipboard button

New button next to Download PNG writes the rendered QR as a PNG Blob
to the system clipboard via the async Clipboard API, with a brief
in-button confirmation (Copied!) or error state.

src/App.vue

@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import { reactive, ref } from 'vue'
+import { computed, reactive, ref } from 'vue'
 import { useQrCode, type QrOptions } from './composables/useQrCode'
 
 const preview = ref<HTMLDivElement | null>(null)
@@ -20,7 +20,25 @@ const options = reactive<QrOptions>({
   hideBackgroundDots: true,
 })
 
-const { download } = useQrCode(preview, options)
+const { download, copyPng } = useQrCode(preview, options)
+
+const copyState = ref<'idle' | 'copied' | 'error'>('idle')
+let copyTimer: number | undefined
+
+async function onCopyPng() {
+  try {
+    await copyPng()
+    copyState.value = 'copied'
+  } catch {
+    copyState.value = 'error'
+  }
+  window.clearTimeout(copyTimer)
+  copyTimer = window.setTimeout(() => (copyState.value = 'idle'), 1800)
+}
+
+const copyLabel = computed(() =>
+  copyState.value === 'copied' ? 'Copied!' : copyState.value === 'error' ? 'Copy failed' : 'Copy PNG',
+)
 
 const dotTypes = ['square', 'dots', 'rounded', 'classy', 'classy-rounded', 'extra-rounded'] as const
 const cornerSquareTypes = ['square', 'dot', 'extra-rounded'] as const
@@ -146,6 +164,14 @@ function clearLogo() {
         </div>
         <div class="download">
           <button type="button" @click="download('png')">Download PNG</button>
+          <button
+            type="button"
+            class="secondary"
+            :class="{ copied: copyState === 'copied', errored: copyState === 'error' }"
+            @click="onCopyPng"
+          >
+            {{ copyLabel }}
+          </button>
           <button type="button" @click="download('svg')">Download SVG</button>
         </div>
       </section>

src/composables/useQrCode.ts

@@ -40,7 +40,14 @@ export function useQrCode(container: Ref<HTMLElement | null>, options: QrOptions
     qr.value?.download({ name: 'qrcode', extension })
   }
 
-  return { download }
+  const copyPng = async () => {
+    if (!qr.value) throw new Error('QR not ready')
+    const data = await qr.value.getRawData('png')
+    if (!(data instanceof Blob)) throw new Error('Unexpected PNG output')
+    await navigator.clipboard.write([new ClipboardItem({ 'image/png': data })])
+  }
+
+  return { download, copyPng }
 }
 
 function toLibOptions(o: QrOptions) {

src/style.css

@@ -203,10 +203,16 @@ input[type="file"] {
 
 .download {
   display: grid;
-  grid-template-columns: 1fr 1fr;
+  grid-template-columns: repeat(3, 1fr);
   gap: 10px;
 }
 
+@media (max-width: 480px) {
+  .download {
+    grid-template-columns: 1fr;
+  }
+}
+
 button {
   font: inherit;
   font-weight: 600;
@@ -240,3 +246,25 @@ button.ghost:hover {
   background: #f1f5f9;
   color: #1e293b;
 }
+
+button.secondary {
+  background: #fff;
+  color: #4f46e5;
+  border-color: #c7d2fe;
+}
+
+button.secondary:hover {
+  background: #eef2ff;
+}
+
+button.secondary.copied {
+  background: #ecfdf5;
+  color: #047857;
+  border-color: #6ee7b7;
+}
+
+button.secondary.errored {
+  background: #fef2f2;
+  color: #b91c1c;
+  border-color: #fecaca;
+}