refactor: Extract all hardcoded content to JSON files

- Move all bilingual text from templates to UI JSON (labels, buttons, modals)
- Move skills summary paragraph to CV JSON with HTML support
- Add new UI sections: navigation, viewControls, sections, footer, portfolio,
  pdfModal, shortcutsModal, infoModal, widgets
- Update Go structs to match expanded JSON structure
- Add template.HTML type for CV.SkillsSummary field
- Add JSON content validation test (70-json-content-validation.test.mjs)

Templates now contain only structural logic (CSS classes, HTML attributes)
while all user-visible text loads from JSON files for proper i18n support.

data/cv-en.json

@@ -2,6 +2,12 @@
   "personal": {
     "name": "Juan Andrés Moreno Rubio",
     "title": "Lead Technical Consultant, FullStack Developer",
+    "titleBadges": [
+      "Technical Consultant",
+      "Full-Stack Engineer",
+      "Authentication Specialist",
+      "Solution Architect"
+    ],
     "location": "Arrecife, Las Palmas de Gran Canaria, Spain",
     "email": "txeo.msx@gmail.com",
     "phone": "+34 676875420",
@@ -12,9 +18,20 @@
     "github": "https://github.com/juanatsap",
     "domestika": "https://www.domestika.org/es/txeo/portfolio",
     "website": "https://juan.andres.morenorub.io",
-    "photo": "/static/images/profile.jpg"
+    "photo": "/static/images/profile.jpg",
+    "firstName": "Juan Andrés",
+    "lastName": "Moreno Rubio",
+    "username": "txeo"
+  },
+  "seo": {
+    "pageTitle": "Curriculum Vitae",
+    "metaTitle": "Professional CV",
+    "metaDescription": "18 years of experience in web development, SAP CDC, React, Node.js, Go, HTMX and AI-assisted development",
+    "ogDescription": "Senior Technical Consultant with 18 years of experience",
+    "keywords": "CV, Resume, FullStack Developer, SAP CDC, React, Node.js, Go, HTMX, AI, Web Development, Technical Consultant"
   },
   "summary": "Full-stack developer specialized in high-availability systems. I've worked on Olympic Games platforms, airport authentication systems with millions of users, and built around 20 websites for diverse sectors (e-commerce, enterprise, institutional). Certified SAP Customer Data Cloud consultant, advising 35-40 international clients on digital identity solutions.",
+  "skillsSummary": "<strong>Full-stack</strong> developer with experience in <strong>Go</strong>, <strong>Node.js</strong>, <strong>React</strong>, and <strong>HTMX</strong> for <strong>modern applications</strong>, plus Java and PHP knowledge for legacy projects. I've worked on <strong>around 20 websites</strong> and provided <strong>consulting for 35-40 international clients</strong>, from e-commerce and enterprise platforms to <strong>authentication systems</strong> managing <strong>millions of users</strong>. Familiar with <strong>AI-assisted development</strong> workflows and infrastructure management (<strong>Linux</strong>, <strong>Docker</strong>, <strong>CI/CD</strong>). I adapt well to both independent work and collaborative teams across different countries.",
   "experience": [
     {
       "position": "Senior SAP Technical Consultant",