feat: self-serve signup Phase 2 (frontend cutover) (#162)

Co-authored-by: Michael Chihlas <michael@resolutionflow.com>
Co-committed-by: Michael Chihlas <michael@resolutionflow.com>

frontend/src/hooks/useFeature.ts

@@ -0,0 +1,16 @@
+import { useBillingStore } from '@/store/billingStore'
+
+/**
+ * Returns whether a feature flag is enabled for the current account.
+ *
+ * Reads from `useBillingStore.enabledFeatures`, which is populated by
+ * `GET /billing/state`. Returns `false` when the flag is absent (closed-by-default).
+ *
+ * The hook subscribes to the store so updates from `refetch()` propagate
+ * without manual refetch in the component.
+ */
+export function useFeature(flagKey: string): boolean {
+  return useBillingStore((state) => Boolean(state.enabledFeatures[flagKey]))
+}
+
+export default useFeature