Add global app state management with context

Introduces AppProvider and related hooks for managing global application state using React context and reducer. Supports loading, error handling, and player data access throughout the app.

Author: JorchCortez

src/state/appStore.tsx

@@ -0,0 +1,67 @@
+import React, { createContext, useContext, useMemo, useReducer } from 'react';
+import type { fullPlayerDataType } from 'types/displayDataTypes';
+
+export type LoadStatus = 'idle' | 'loading' | 'ready' | 'error';
+
+interface AppState {
+    status: LoadStatus;
+    loadedAt?: number;
+    saveSignature?: string;
+    players: fullPlayerDataType[];
+    error?: string;
+}
+
+const initialState: AppState = {
+    status: 'idle',
+    players: [],
+};
+
+    type AppAction =
+    | { type: 'loadSaveRequested'; payload?: { fileName?: string } }
+    | { type: 'loadSaveSucceeded'; payload: { saveSignature: string; players: fullPlayerDataType[] } }
+    | { type: 'loadSaveFailed'; payload: { error: string | undefined } }
+    | { type: 'clearSave' };
+
+function appReducer(state: AppState, action: AppAction): AppState {
+    switch (action.type) {
+        case 'loadSaveRequested':
+        return { ...state, status: 'loading' };
+        case 'loadSaveSucceeded':
+        return {
+            status: 'ready',
+            loadedAt: Date.now(),
+            saveSignature: action.payload.saveSignature,
+            players: action.payload.players,
+        };
+        case 'loadSaveFailed':
+        return { ...state, status: 'error', error: action.payload.error ?? undefined };
+        case 'clearSave':
+        return { ...initialState };
+        default:
+        return state;
+    }
+}
+
+const AppContext = createContext<{ state: AppState; dispatch: React.Dispatch<AppAction> } | undefined>(undefined);
+
+export const AppProvider: React.FC<React.PropsWithChildren> = ({ children }) => {
+  const [state, dispatch] = useReducer(appReducer, initialState);
+  const value = useMemo(() => ({ state, dispatch }), [state]);
+  return <AppContext.Provider value={value}>{children}</AppContext.Provider>;
+};
+
+export const useAppStore = () => {
+  const ctx = useContext(AppContext);
+  if (!ctx) throw new Error('useAppStore must be used within AppProvider');
+  return ctx;
+};
+
+export const useAppSelector = <T,>(select: (s: AppState) => T): T => {
+  const { state } = useAppStore();
+  return select(state);
+};
+
+// Example selectors
+export const usePlayers = () => useAppSelector(s => s.players);
+export const useLoadStatus = () => useAppSelector(s => s.status);
+export const usePlayerByName = (name: string) => useAppSelector(s => s.players.find(p => p.playerName === name));