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.

templates/partials/sections/experience.html

@@ -7,7 +7,7 @@
             <summary>
                 <h3 class="section-title">
                     <iconify-icon icon="mdi:office-building" width="24" height="24" class="section-icon"></iconify-icon>
-                    {{if eq .Lang "es"}}Experiencia{{else}}Experience{{end}}
+                    {{.UI.Navigation.Experience}}
                 </h3>
             </summary>
 
@@ -22,10 +22,10 @@
             </div>
             <div class="experience-content">
                 <strong>{{.Position}}{{if .Company}} - {{if .CompanyURL}}<a href="{{.CompanyURL}}" target="_blank" rel="noopener noreferrer">{{.Company}}</a>{{else}}{{.Company}}{{end}}{{if .Duration}} - <span class="duration-text">{{.Duration}}</span>{{end}}{{end}}</strong>
-                {{if .Current}}<span class="current-badge">{{if eq $.Lang "es"}}ACTUAL{{else}}CURRENT{{end}}</span>{{end}}
-                {{if .Expired}}<span class="expired-badge">{{if eq $.Lang "es"}}EXPIRADO{{else}}EXPIRED{{end}}</span>{{end}}
+                {{if .Current}}<span class="current-badge">{{$.UI.Sections.CurrentBadge}}</span>{{end}}
+                {{if .Expired}}<span class="expired-badge">{{$.UI.Sections.ExpiredBadge}}</span>{{end}}
                 <br>
-                <small>{{.StartDate}} / {{if .Current}}{{if eq $.Lang "es"}}presente{{else}}now{{end}}{{else}}{{.EndDate}}{{end}} - ({{.Location}})</small>
+                <small>{{.StartDate}} / {{if .Current}}{{$.UI.Sections.Present}}{{else}}{{.EndDate}}{{end}} - ({{.Location}})</small>
 
                 {{if .ShortDescription}}
                 <p class="experience-desc short-desc">{{.ShortDescription | safeHTML}}</p>