Add RSVP context and provider for managing RSVP state

Introduce a context and provider for handling RSVP data, including fetching, updating, creating, and deleting RSVPs. The implementation utilizes React Query for data management and exposes methods for managing RSVP operations throughout the application.

frontend/src/providers/data.tsx

@@ -1,11 +1,14 @@
 import React from "react";
 import { EventsProvider } from "@/context/event-context";
 import { EventThemesProvider } from "@/context/event-theme-context";
+import { RSVPProvider } from "@/context/rsvp-context";
 
 export function DataProviders({ children }: { children: React.ReactNode }) {
   return (
     <EventThemesProvider>
-      <EventsProvider>{children}</EventsProvider>
+      <EventsProvider>
+        <RSVPProvider>{children}</RSVPProvider>
+      </EventsProvider>
     </EventThemesProvider>
   );
 }