chore: add theme context

Author: Ayan-Nalawade

gs/frontend/mcc/src/contexts/ThemeContext.tsx

@@ -0,0 +1,53 @@
+import { createContext, useContext, useEffect, useState } from "react";
+
+type Theme = "light" | "dark";
+
+interface ThemeContextType {
+  theme: Theme;
+  toggleTheme: () => void;
+}
+
+const ThemeContext = createContext<ThemeContextType | undefined>(undefined);
+
+export function ThemeProvider({ children }: { children: React.ReactNode }) {
+
+  const [theme, setTheme] = useState<Theme>(() => {
+    const stored = localStorage.getItem("theme") as Theme | null;
+    if (stored) return stored;
+
+
+    if (window.matchMedia("(prefers-color-scheme: dark)").matches) { // Find system Preference
+      return "dark";
+    }
+    return "light";
+  });
+
+
+  useEffect(() => {
+    const root = document.documentElement;
+    if (theme === "dark") {
+      root.classList.add("dark");
+    } else {
+      root.classList.remove("dark");
+    }
+    localStorage.setItem("theme", theme);
+  }, [theme]);
+
+  const toggleTheme = () => {
+    setTheme((prev) => (prev === "light" ? "dark" : "light"));
+  };
+
+  return (
+    <ThemeContext.Provider value={{ theme, toggleTheme }}>
+      {children}
+    </ThemeContext.Provider>
+  );
+}
+
+export function useTheme() {
+  const context = useContext(ThemeContext);
+  if (!context) {
+    throw new Error("useTheme must be used within ThemeProvider");
+  }
+  return context;
+}