Refactor context and provider structure for improved organization and maintainability

- Removed individual context files for Auth, Flyers, MasterItems, Modal, UserData, and their respective hooks.
- Introduced centralized provider files for each context, encapsulating logic and state management.
- Updated imports across the application to reflect the new structure, ensuring all hooks and contexts are correctly referenced.
- Enhanced the AppProviders component to streamline the wrapping of all context providers in the application.
- Improved type definitions and context management for better type safety and clarity.

src/hooks/useWatchedItems.tsx

@@ -1,8 +1,8 @@
 // src/hooks/useWatchedItems.tsx
 import { useMemo, useCallback } from 'react';
-import { useAuth } from '../contexts/AuthContext';
+import { useAuth } from '../hooks/useAuth';
 import { useApi } from './useApi';
-import { useUserData } from './useUserData';
+import { useUserData } from '../hooks/useUserData';
 import * as apiClient from '../services/apiClient';
 import type { MasterGroceryItem } from '../types';