Initial commit: Complete NodeJS-native setup

- Migrated from Python pre-commit to NodeJS-native solution
- Reorganized documentation structure
- Set up Husky + lint-staged for efficient pre-commit hooks
- Fixed Dockerfile healthcheck issue
- Added comprehensive documentation index

hooks/useTheme.ts

@@ -0,0 +1,43 @@
+import { useEffect, useMemo } from 'react';
+import { useLocalStorage } from './useLocalStorage';
+
+type Theme = 'light' | 'dark' | 'system';
+
+export function useTheme() {
+  const [theme, setTheme] = useLocalStorage<Theme>('theme', 'system');
+
+  const systemTheme = useMemo(() => {
+    if (typeof window !== 'undefined' && window.matchMedia) {
+      return window.matchMedia('(prefers-color-scheme: dark)').matches
+        ? 'dark'
+        : 'light';
+    }
+    return 'light';
+  }, []);
+
+  const applyTheme = () => {
+    const themeToApply = theme === 'system' ? systemTheme : theme;
+    const root = window.document.documentElement;
+    root.classList.remove('light', 'dark');
+    root.classList.add(themeToApply);
+  };
+
+  useEffect(() => {
+    const mediaQuery = window.matchMedia('(prefers-color-scheme: dark)');
+    const handleChange = () => {
+      if (theme === 'system') {
+        applyTheme();
+      }
+    };
+    mediaQuery.addEventListener('change', handleChange);
+    return () => mediaQuery.removeEventListener('change', handleChange);
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [theme]);
+
+  useEffect(() => {
+    applyTheme();
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [theme, systemTheme]);
+
+  return { theme, setTheme };
+}