Initial commit: SQL audit platform v0.1.0

FastAPI backend with auth, user, instance, ticket, query, dashboard APIs.
React + TypeScript frontend with mock data UI (10 pages).
SQLite + async SQLAlchemy, JWT auth, role-based access control.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/hooks/useTheme.tsx

@@ -0,0 +1,61 @@
+import { createContext, useContext, useState, useCallback, useMemo, useEffect } from 'react';
+
+export type Theme = 'dark' | 'light';
+
+interface ThemeContextType {
+  theme: Theme;
+  toggleTheme: () => void;
+  setTheme: (theme: Theme) => void;
+  isDark: boolean;
+  isLight: boolean;
+}
+
+const ThemeContext = createContext<ThemeContextType | null>(null);
+
+function getInitialTheme(): Theme {
+  if (typeof window === 'undefined') return 'dark';
+  const stored = localStorage.getItem('dg-theme') as Theme | null;
+  if (stored === 'dark' || stored === 'light') return stored;
+  return 'dark';
+}
+
+function applyTheme(theme: Theme) {
+  document.documentElement.setAttribute('data-theme', theme);
+}
+
+export function ThemeProvider({ children }: { children: React.ReactNode }) {
+  const [theme, setThemeState] = useState<Theme>(getInitialTheme);
+
+  useEffect(() => {
+    applyTheme(theme);
+  }, [theme]);
+
+  const toggleTheme = useCallback(() => {
+    setThemeState(prev => {
+      const next = prev === 'dark' ? 'light' : 'dark';
+      localStorage.setItem('dg-theme', next);
+      return next;
+    });
+  }, []);
+
+  const setTheme = useCallback((t: Theme) => {
+    localStorage.setItem('dg-theme', t);
+    setThemeState(t);
+  }, []);
+
+  const value = useMemo(() => ({
+    theme,
+    toggleTheme,
+    setTheme,
+    isDark: theme === 'dark',
+    isLight: theme === 'light',
+  }), [theme, toggleTheme, setTheme]);
+
+  return <ThemeContext.Provider value={value}>{children}</ThemeContext.Provider>;
+}
+
+export function useTheme(): ThemeContextType {
+  const ctx = useContext(ThemeContext);
+  if (!ctx) throw new Error('useTheme must be used within ThemeProvider');
+  return ctx;
+}