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src/contexts/ThemeContext.jsx

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+import React, { createContext, useContext, useState, useEffect } from 'react';
+
+const ThemeContext = createContext();
+
+export const ThemeProvider = ({ children }) => {
+  const [isDarkMode, setIsDarkMode] = useState(() => {
+    const savedTheme = localStorage.getItem('theme');
+    return savedTheme === 'dark' || (savedTheme === null && window.matchMedia('(prefers-color-scheme: dark)').matches);
+  });
+
+  useEffect(() => {
+    localStorage.setItem('theme', isDarkMode ? 'dark' : 'light');
+    document.documentElement.classList.toggle('dark', isDarkMode);
+  }, [isDarkMode]);
+
+  const toggleTheme = () => {
+    setIsDarkMode(!isDarkMode);
+  };
+
+  return (
+    <ThemeContext.Provider value={{ isDarkMode, toggleTheme }}>
+      {children}
+    </ThemeContext.Provider>
+  );
+};
+
+export const useTheme = () => {
+  const context = useContext(ThemeContext);
+  if (!context) {
+    throw new Error('useTheme must be used within a ThemeProvider');
+  }
+  return context;
+};