Instant env switch: invalidate all queries on environment change

EnvironmentContext holds current env as React state. On change,
QueryInvalidatorOnEnvChange calls queryClient.invalidateQueries() so
all content/list pages refetch immediately without manual reload.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

admin-ui/src/lib/EnvironmentContext.tsx

@@ -0,0 +1,37 @@
+"use client";
+
+import { createContext, useContext, useState, useEffect, type ReactNode } from "react";
+import { getCurrentEnvironment, setCurrentEnvironment } from "@/lib/api";
+
+type EnvironmentContextType = {
+  environment: string | null;
+  setEnvironment: (env: string) => void;
+};
+
+const EnvironmentContext = createContext<EnvironmentContextType>({
+  environment: null,
+  setEnvironment: () => {},
+});
+
+export function EnvironmentProvider({ children }: { children: ReactNode }) {
+  const [environment, setEnv] = useState<string | null>(null);
+
+  useEffect(() => {
+    setEnv(getCurrentEnvironment());
+  }, []);
+
+  function setEnvironment(env: string) {
+    setCurrentEnvironment(env);
+    setEnv(env);
+  }
+
+  return (
+    <EnvironmentContext.Provider value={{ environment, setEnvironment }}>
+      {children}
+    </EnvironmentContext.Provider>
+  );
+}
+
+export function useEnvironment() {
+  return useContext(EnvironmentContext);
+}