Add GuestContext for managing guest-related state

Introduced a new GuestContext with accompanying provider to handle guest-related data, including fetching, creating, updating, and deleting guests. Integrated GuestsProvider into the application's data provider hierarchy to ensure guest data is accessible across components.

frontend/src/providers/data.tsx

@@ -2,12 +2,15 @@ import React from "react";
 import { EventsProvider } from "@/context/event-context";
 import { EventThemesProvider } from "@/context/event-theme-context";
 import { RSVPProvider } from "@/context/rsvp-context";
+import { GuestsProvider } from "@/context/guest-context";
 
 export function DataProviders({ children }: { children: React.ReactNode }) {
   return (
     <EventThemesProvider>
       <EventsProvider>
-        <RSVPProvider>{children}</RSVPProvider>
+        <GuestsProvider>
+          <RSVPProvider>{children}</RSVPProvider>
+        </GuestsProvider>
       </EventsProvider>
     </EventThemesProvider>
   );