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.

plugins/supabase.client.ts

@@ -0,0 +1,27 @@
+import { createClient, type SupabaseClient } from "@supabase/supabase-js";
+import { defineNuxtPlugin, useRuntimeConfig } from "nuxt/app";
+
+export default defineNuxtPlugin((nuxtApp) => {
+  const { url, anonKey } = useRuntimeConfig().public.supabase;
+
+  if (!url || !anonKey) {
+    if (process.env.NODE_ENV !== "production") {
+      console.warn(
+        "Supabase configuration is incomplete. Set SUPABASE_URL and SUPABASE_ANON_KEY in your environment."
+      );
+    }
+
+    nuxtApp.provide("supabase", null);
+    return;
+  }
+
+  const supabase = createClient(url, anonKey, {
+    auth: {
+      persistSession: true,
+      storageKey: "slipmatz.supabase.auth",
+    },
+  });
+
+  nuxtApp.provide("supabase", supabase);
+  nuxtApp.vueApp.config.globalProperties.$supabase = supabase;
+});