Preserve QPowerPoint slide backgrounds

src/App.tsx

@@ -13,6 +13,7 @@ const STORAGE_KEY = "qoffice-state-v1";
 function migrateQOfficeState(state: QOfficeState): QOfficeState {
   const launchChecklistAttachments = initialState.mail.messages.find((message) => message.id === "mail-1")?.attachments;
   const sampleSheet = initialState.workbook.sheets.find((sheet) => sheet.id === "sheet-1");
+  const sampleSlidesById = Object.fromEntries(initialState.deck.slides.map((slide) => [slide.id, slide]));
   const sampleWordHtml = initialState.word.html;
   const needsSampleWordColor =
     state.word.id === initialState.word.id &&
@@ -64,11 +65,25 @@ function migrateQOfficeState(state: QOfficeState): QOfficeState {
         })
       : state.workbook.sheets;
 
+  const slides =
+    state.deck.id === initialState.deck.id
+      ? state.deck.slides.map((slide) => {
+          const sampleSlide = sampleSlidesById[slide.id];
+          if (!sampleSlide?.backgroundColor || slide.backgroundColor) {
+            return slide;
+          }
+
+          changed = true;
+          return { ...slide, backgroundColor: sampleSlide.backgroundColor };
+        })
+      : state.deck.slides;
+
   return changed
     ? {
         ...state,
         word: needsSampleWordColor ? { ...state.word, html: sampleWordHtml } : state.word,
         workbook: { ...state.workbook, sheets },
+        deck: { ...state.deck, slides },
         mail: { ...state.mail, messages }
       }
     : state;