✨ feat: enhance admin UI configuration and SSR handling

- Add support for number chip arrays and JSON editor in admin UI config.
- Introduce pagebuilder block registry for Svelte components in admin previews.
- Implement custom role names and a 3-layer cascade model for field-level permissions.
- Add CORS configuration hierarchy for better API security.
- Update project setup instructions for admin token and config management.
- Improve SSR 404 signaling with proper context handling in NotFound component.
- Refactor routing structure to separate NotFound page into its own route.

frontend/src/routes/NotFound.svelte

@@ -0,0 +1,34 @@
+<script lang="ts">
+    import { _ } from "../lib/i18n/index"
+    import { localizedPath } from "../lib/i18n"
+    import { reveal } from "../lib/actions/reveal"
+
+    // Signal HTTP 404 to the SSR hook during server-side rendering.
+    // get_read.js checks context.is404 after render() and returns status 404.
+    if (typeof window === "undefined") {
+        // @ts-ignore - context is the goja global in SSR runtime (declared by tibi-types)
+        context.is404 = true
+    }
+</script>
+
+<section class="min-h-[60vh] flex items-center justify-center bg-gray-50">
+    <div class="text-center px-6 py-20" use:reveal>
+        <div class="text-8xl mb-6 opacity-20 font-display font-black text-brand-900">404</div>
+        <h1 class="text-3xl sm:text-4xl font-display font-bold text-gray-900 mb-4">
+            {$_("page.notFound.title")}
+        </h1>
+        <p class="text-lg text-gray-500 mb-8 max-w-md mx-auto">
+            {$_("page.notFound.text")}
+        </p>
+        <a
+            href={localizedPath("/")}
+            class="inline-flex items-center gap-2 bg-brand-600 hover:bg-brand-700 text-white font-bold px-8 py-4 rounded-xl text-lg transition-all duration-300 hover:shadow-lg hover:shadow-brand-500/25 hover:-translate-y-0.5"
+        >
+            <svg class="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M10 19l-7-7m0 0l7-7m-7 7h18"
+                ></path>
+            </svg>
+            {$_("page.notFound.backHome")}
+        </a>
+    </div>
+</section>