Tag blog posts and sign them with a member

Tags are named in every language and made from the page form; the byline is
the member who signs a post on the site. The public API sends both, filters
posts by tag and lists the tags in use.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/Feature/Api/PublicApiContractTest.php

@@ -10,6 +10,7 @@ use App\Models\Member;
 use App\Models\Page;
 use App\Models\Project;
 use App\Models\Service;
+use App\Models\Tag;
 use App\Models\Talk;
 use App\Models\Technology;
 use App\Models\Testimonial;
@@ -59,10 +60,12 @@ class PublicApiContractTest extends TestCase
             'slug' => ['es' => 'mi-proyecto'],
         ]);
 
-        Page::factory()->published()->create([
+        $page = Page::factory()->published()->create([
             'title' => ['es' => 'Quiénes somos'],
             'slug' => ['es' => 'quienes-somos'],
+            'byline_member_id' => Member::factory()->create(['is_public' => true])->id,
         ]);
+        $page->tags()->attach(Tag::factory()->create());
 
         Member::factory()->create([
             'name' => 'Ada Lovelace',