feat: implement app content readiness handling in page and components

- Added `appContentReady` state to manage visibility of app content once loading is complete.
- Updated `useEffect` hooks in `CurrentDutyView` and `CalendarPage` to signal when content is ready, enhancing user experience by hiding native loading indicators.
- Refactored `Home` component to conditionally render content based on `appContentReady`, ensuring a smoother transition for users.
- Enhanced app store to include `setAppContentReady` method for state management.

webapp-next/src/store/app-store.ts

@@ -28,6 +28,8 @@ export interface AppState {
   accessDeniedDetail: string | null;
   currentView: CurrentView;
   selectedDay: string | null;
+  /** True when the first visible screen has finished loading; used to hide content until ready(). */
+  appContentReady: boolean;
 
   setCurrentMonth: (d: Date) => void;
   nextMonth: () => void;
@@ -41,8 +43,9 @@ export interface AppState {
   setLang: (v: "ru" | "en") => void;
   setCurrentView: (v: CurrentView) => void;
   setSelectedDay: (key: string | null) => void;
+  setAppContentReady: (v: boolean) => void;
   /** Batch multiple state updates into a single re-render. */
-  batchUpdate: (partial: Partial<Pick<AppState, "currentMonth" | "pendingMonth" | "lang" | "duties" | "calendarEvents" | "dataForMonthKey" | "loading" | "error" | "accessDenied" | "accessDeniedDetail" | "currentView" | "selectedDay">>) => void;
+  batchUpdate: (partial: Partial<Pick<AppState, "currentMonth" | "pendingMonth" | "lang" | "duties" | "calendarEvents" | "dataForMonthKey" | "loading" | "error" | "accessDenied" | "accessDeniedDetail" | "currentView" | "selectedDay" | "appContentReady">>) => void;
 }
 
 const now = new Date();
@@ -67,6 +70,7 @@ export const useAppStore = create<AppState>((set) => ({
   accessDeniedDetail: null,
   currentView: getInitialView(),
   selectedDay: null,
+  appContentReady: false,
 
   setCurrentMonth: (d) => set({ currentMonth: d }),
   nextMonth: () =>
@@ -86,5 +90,6 @@ export const useAppStore = create<AppState>((set) => ({
   setLang: (v) => set({ lang: v }),
   setCurrentView: (v) => set({ currentView: v }),
   setSelectedDay: (key) => set({ selectedDay: key }),
+  setAppContentReady: (v) => set({ appContentReady: v }),
   batchUpdate: (partial) => set(partial),
 }));