feat: add design persistence functionality with Auth0 and Supabase integration

- Implemented `useDesignPersistence` composable for managing design records.
- Enhanced `useSlipmatDesigner` to support loading designs from JSON.
- Created global authentication middleware for route protection.
- Added Supabase client plugin for database interactions.
- Developed API endpoints for fetching, saving, and retrieving designs.
- Introduced utility functions for Auth0 token verification and Supabase client retrieval.
- Updated Nuxt configuration to include Auth0 and Supabase environment variables.
- Added necessary dependencies for Auth0 and Supabase.
- Enhanced TypeScript configuration for improved type support.

server/utils/supabase.ts

@@ -0,0 +1,34 @@
+import { createClient, type SupabaseClient } from "@supabase/supabase-js";
+import { createError } from "h3";
+import { useRuntimeConfig } from "#imports";
+
+const globalKey = Symbol.for("slipmatz.supabase.serviceClient");
+
+type GlobalWithSupabase = typeof globalThis & {
+  [globalKey]?: SupabaseClient;
+};
+
+export const getSupabaseServiceClient = (): SupabaseClient => {
+  const config = useRuntimeConfig();
+  const supabaseUrl = config.public.supabase?.url;
+  const serviceRoleKey = config.supabase?.serviceRoleKey;
+
+  if (!supabaseUrl || !serviceRoleKey) {
+    throw createError({
+      statusCode: 500,
+      statusMessage: "Supabase environment variables are not configured.",
+    });
+  }
+
+  const scope = globalThis as GlobalWithSupabase;
+  if (!scope[globalKey]) {
+    scope[globalKey] = createClient(supabaseUrl, serviceRoleKey, {
+      auth: {
+        autoRefreshToken: false,
+        persistSession: false,
+      },
+    });
+  }
+
+  return scope[globalKey]!;
+};