Add Command Center v2: DQ/RAG integration, S3 browser, Jupyter, GPU matrix.

Mirror mo/atc-GPU layout with config/, docs/, scripts/ for Gitea deploy.

ui/src/context/ThemeContext.tsx

@@ -0,0 +1,44 @@
+import { createContext, useContext, useEffect, useState, type ReactNode } from 'react'
+
+export type Theme = 'light' | 'dark'
+
+type ThemeContextValue = {
+  theme: Theme
+  toggle: () => void
+}
+
+const ThemeContext = createContext<ThemeContextValue | null>(null)
+const STORAGE_KEY = 'atc-command-center-theme'
+
+function readStored(): Theme {
+  const v = localStorage.getItem(STORAGE_KEY)
+  return v === 'dark' || v === 'light' ? v : 'light'
+}
+
+export function ThemeProvider({ children }: { children: ReactNode }) {
+  const [theme, setTheme] = useState<Theme>(() => {
+    if (typeof window === 'undefined') return 'light'
+    return readStored()
+  })
+
+  useEffect(() => {
+    const root = document.documentElement
+    root.classList.remove('light', 'dark')
+    root.classList.add(theme)
+    localStorage.setItem(STORAGE_KEY, theme)
+  }, [theme])
+
+  const toggle = () => setTheme((t) => (t === 'light' ? 'dark' : 'light'))
+
+  return (
+    <ThemeContext.Provider value={{ theme, toggle }}>
+      {children}
+    </ThemeContext.Provider>
+  )
+}
+
+export function useTheme() {
+  const ctx = useContext(ThemeContext)
+  if (!ctx) throw new Error('useTheme outside ThemeProvider')
+  return ctx
+}