refactor: reorganize imports and improve error handling across components

frontend/src/hooks/useTheme.ts

@@ -0,0 +1,10 @@
+import { useContext } from 'react'
+import { ThemeContext } from '../context/ThemeContextValue'
+
+export function useTheme() {
+  const context = useContext(ThemeContext)
+  if (context === undefined) {
+    throw new Error('useTheme must be used within a ThemeProvider')
+  }
+  return context
+}