feat(railpack): add config merging, beta badge, and nodejs seeder example

- Implement railpack.json + generated config deep merging logic in
  ApplicationDeploymentJob with JSON validation and assoc array checks
- Label Railpack as "Beta" in all build pack selectors and show a
  visible beta badge when railpack is selected in new-app forms
- Add railpack-nodejs Fastify example to ApplicationSeeder
- Add ApplicationSeederTest and ApplicationDeploymentRailpackConfigTest
  covering config merge behavior and seeder correctness

resources/views/livewire/project/new/github-private-repository.blade.php

@@ -83,7 +83,7 @@
                                     </x-forms.select>
                                     <x-forms.select wire:model.live="build_pack" label="Build Pack" required>
                                         <option value="nixpacks">Nixpacks</option>
-                                        <option value="railpack">Railpack</option>
+                                        <option value="railpack">Railpack (Beta)</option>
                                         <option value="static">Static</option>
                                         <option value="dockerfile">Dockerfile</option>
                                         <option value="dockercompose">Docker Compose</option>
@@ -93,6 +93,14 @@
                                             helper="If there is a build process involved (like Svelte, React, Next, etc..), please specify the output directory for the build assets." />
                                     @endif
                                 </div>
+                                @if ($build_pack === 'railpack')
+                                    <div>
+                                        <span
+                                            class="px-2 py-1 text-xs font-bold uppercase tracking-wide bg-coollabs/10 dark:bg-warning/20 text-coollabs dark:text-warning rounded">
+                                            Beta
+                                        </span>
+                                    </div>
+                                @endif
                                 @if ($build_pack === 'dockercompose')
                                     <div x-data="{
                                         baseDir: '{{ $base_directory }}',