feat: add Cmd/Ctrl+P shortcut to trigger print preview

Added Cmd+P (Mac) or Ctrl+P (Windows/Linux) to trigger printPreview():
- Prevents default browser print dialog
- Triggers custom print preview function
- Updated print button tooltip to show keyboard shortcut
- Added platform detection for correct symbol display (⌘ or Ctrl)

Works in all contexts (main document and iframe).

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/App.vue

@@ -38,6 +38,9 @@ const activeFrame = computed(() => {
     : previewFrame2.value;
 });
 
+// Detect platform for keyboard shortcut display
+const isMac = typeof navigator !== 'undefined' && navigator.platform.toUpperCase().indexOf('MAC') >= 0;
+
 // Handle keyboard shortcuts
 const handleKeyboardShortcut = (event) => {
   // Escape key - close any open popup
@@ -60,6 +63,13 @@ const handleKeyboardShortcut = (event) => {
     return;
   }
 
+  // Cmd+P (Mac) or Ctrl+P (Windows/Linux) - print
+  if ((event.metaKey || event.ctrlKey) && event.key === 'p') {
+    event.preventDefault();
+    printPreview();
+    return;
+  }
+
   // Cmd+S (Mac) or Ctrl+S (Windows/Linux) - save
   if ((event.metaKey || event.ctrlKey) && event.key === 's') {
     event.preventDefault();
@@ -645,7 +655,7 @@ onUnmounted(() => {
     @close="handlePagePopupClose"
   />
 
-  <button class="print-btn" @click="printPreview" title="Imprimer">
+  <button class="print-btn" @click="printPreview" :title="`Imprimer (${isMac ? '⌘' : 'Ctrl'}+P)`">
     <svg
       xmlns="http://www.w3.org/2000/svg"
       viewBox="0 0 24 24"