feat: add sharing feature

src/state.ts

@@ -1,15 +1,19 @@
-import { DailyTotalCalories, FoodItem } from "./types";
+import { DailyTotalCalories, FoodItem, SharedDay } from "./types";
 
 interface AppState {
   currentHighlightIndex: number;
   searchTimeout: number | null;
   searchResults: FoodItem[];
   calendarMonthlyCalories: DailyTotalCalories[];
+  isSharedView: boolean;
+  sharedData: SharedDay | null;
 }
 
 export const appState: AppState = {
   currentHighlightIndex: -1,
   searchTimeout: null,
   searchResults: [],
-  calendarMonthlyCalories: []
+  calendarMonthlyCalories: [],
+  isSharedView: false,
+  sharedData: null
 };