feat: implement component-level skeleton loaders for language transitions

Implemented dual-state skeleton system as specified in prompt:
- Each component has actual-content + skeleton-content structure
- CSS toggles visibility via .loading class on component-wrapper
- Individual skeleton boxes (name, photo, intro, etc.) with shimmer animation
- Hyperscript triggers loading state during language switch

Changes:
- skeleton.css: Complete component-level skeleton CSS system with shimmer
- language-selector.html: Hyperscript to add/remove .loading class
- header.html: Dual-state structure with skeleton placeholders

Behavior:
- Click language button → .loading class added to components
- Actual content fades out (opacity → 0) in 250ms
- Skeleton boxes appear and shimmer
- After HTMX swap + 100ms delay → .loading class removed
- New content fades in (opacity → 1) in 250ms

Test Results:
✅ Component wrapper structure verified
✅ Dual-state toggle working correctly
✅ Skeleton elements present and animated
✅ Shimmer animation active (1.8s infinite loop)
✅ Accessibility: respects prefers-reduced-motion
✅ Print: skeletons hidden, content always visible

Next: Add skeleton structure to remaining components (experience, education, skills, projects)

static/css/skeleton.css

@@ -1,36 +1,29 @@
 /**
- * Skeleton Loader for Language Transitions
+ * Component-Level Skeleton Loaders for Language Transitions
- * ==========================================
+ * ==========================================================
- * Simple skeleton animation shown during HTMX content swaps
+ * Each CV component has dual-state structure:
- * Uses HTMX's built-in .htmx-swapping class
+ * - .actual-content (real CV content)
+ * - .skeleton-content (gray pulsing placeholders)
+ *
+ * Loading state controlled via .loading class on component wrapper
  */
 
 /* ========================================================================
-   CONTENT FADE & SKELETON TRANSITION
+   BASE SKELETON STYLES
    ======================================================================== */
 
-/* Fade out content when HTMX starts swapping */
+.skeleton {
-.cv-page-content-wrapper.htmx-swapping {
+  background: linear-gradient(
-  opacity: 0.3;
+    90deg,
-  transition: opacity 250ms ease;
+    #f0f0f0 0%,
-  position: relative;
+    #e8e8e8 20%,
-}
+    #f0f0f0 40%,
-
+    #f0f0f0 100%
-/* Skeleton overlay appears during swap */
+  );
-.cv-page-content-wrapper.htmx-swapping::before {
-  content: "";
-  position: absolute;
-  top: 0;
-  left: 0;
-  right: 0;
-  bottom: 0;
-  background:
-    linear-gradient(90deg, #f0f0f0 25%, #e8e8e8 50%, #f0f0f0 75%);
   background-size: 200% 100%;
-  animation: skeleton-shimmer 1.5s ease-in-out infinite;
+  animation: skeleton-shimmer 1.8s ease-in-out infinite;
   border-radius: 4px;
-  pointer-events: none;
+  will-change: background-position;
-  z-index: 1;
 }
 
 @keyframes skeleton-shimmer {
@@ -42,23 +35,294 @@
   }
 }
 
-/* Fade in new content */
+/* ========================================================================
-.cv-page-content-wrapper.htmx-settling {
+   COMPONENT WRAPPER STATE TOGGLING
+   ======================================================================== */
+
+/* Default state: Show actual content, hide skeleton */
+.component-wrapper {
+  position: relative;
+}
+
+.component-wrapper .actual-content {
   opacity: 1;
-  transition: opacity 250ms ease;
+  transition: opacity 250ms ease-out;
+}
+
+.component-wrapper .skeleton-content {
+  position: absolute;
+  top: 0;
+  left: 0;
+  right: 0;
+  opacity: 0;
+  pointer-events: none;
+  transition: opacity 250ms ease-out;
+}
+
+/* Loading state: Hide actual content, show skeleton */
+.component-wrapper.loading .actual-content {
+  opacity: 0;
+  pointer-events: none;
+}
+
+.component-wrapper.loading .skeleton-content {
+  opacity: 1;
+  pointer-events: all;
 }
 
 /* ========================================================================
-   ACCESSIBILITY
+   SKELETON SHAPE DEFINITIONS
+   ======================================================================== */
+
+/* Header Section Skeleton */
+.skeleton-header {
+  display: flex;
+  gap: 20px;
+  margin-bottom: 20px;
+}
+
+.skeleton-header-text {
+  flex: 1;
+}
+
+.skeleton-name {
+  height: 32px;
+  width: 70%;
+  margin-bottom: 8px;
+}
+
+.skeleton-experience-years {
+  height: 20px;
+  width: 50%;
+  margin-bottom: 16px;
+}
+
+.skeleton-photo {
+  width: 120px;
+  height: 120px;
+  border-radius: 50%;
+  flex-shrink: 0;
+}
+
+.skeleton-intro {
+  height: 60px;
+  width: 100%;
+  margin-top: 12px;
+}
+
+/* Section Title Skeleton */
+.skeleton-section-title {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  margin-bottom: 16px;
+}
+
+.skeleton-icon {
+  width: 24px;
+  height: 24px;
+  border-radius: 4px;
+  flex-shrink: 0;
+}
+
+.skeleton-title-text {
+  height: 24px;
+  width: 40%;
+}
+
+/* Skill Item Skeleton (Sidebar) */
+.skeleton-skill-category {
+  margin-bottom: 20px;
+}
+
+.skeleton-skill-title {
+  height: 20px;
+  width: 60%;
+  margin-bottom: 12px;
+}
+
+.skeleton-skill-items {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.skeleton-skill-item {
+  height: 32px;
+  width: 100%;
+}
+
+.skeleton-skill-item:nth-child(2) {
+  width: 85%;
+}
+
+.skeleton-skill-item:nth-child(3) {
+  width: 90%;
+}
+
+.skeleton-skill-item:nth-child(4) {
+  width: 75%;
+}
+
+/* Experience Entry Skeleton */
+.skeleton-experience-item {
+  display: flex;
+  gap: 16px;
+  margin-bottom: 24px;
+}
+
+.skeleton-company-logo {
+  width: 60px;
+  height: 60px;
+  border-radius: 8px;
+  flex-shrink: 0;
+}
+
+.skeleton-experience-content {
+  flex: 1;
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.skeleton-position {
+  height: 20px;
+  width: 80%;
+}
+
+.skeleton-company-info {
+  height: 16px;
+  width: 60%;
+}
+
+.skeleton-description {
+  height: 40px;
+  width: 100%;
+  margin-top: 4px;
+}
+
+.skeleton-description.short {
+  width: 85%;
+}
+
+/* Education Item Skeleton */
+.skeleton-education-item {
+  margin-bottom: 16px;
+}
+
+.skeleton-degree {
+  height: 18px;
+  width: 75%;
+  margin-bottom: 6px;
+}
+
+.skeleton-institution {
+  height: 16px;
+  width: 50%;
+}
+
+/* Text Block Skeletons (Generic) */
+.skeleton-text {
+  height: 16px;
+  margin-bottom: 8px;
+}
+
+.skeleton-text.short {
+  width: 60%;
+}
+
+.skeleton-text.medium {
+  width: 80%;
+}
+
+.skeleton-text.long {
+  width: 95%;
+}
+
+/* ========================================================================
+   RESPONSIVE ADJUSTMENTS
+   ======================================================================== */
+
+@media (max-width: 768px) {
+  .skeleton-header {
+    flex-direction: column;
+    align-items: center;
+  }
+
+  .skeleton-header-text {
+    text-align: center;
+    width: 100%;
+  }
+
+  .skeleton-name,
+  .skeleton-experience-years {
+    width: 80%;
+    margin-left: auto;
+    margin-right: auto;
+  }
+
+  .skeleton-photo {
+    width: 100px;
+    height: 100px;
+  }
+
+  .skeleton-experience-item {
+    flex-direction: column;
+    gap: 12px;
+  }
+
+  .skeleton-company-logo {
+    width: 50px;
+    height: 50px;
+  }
+}
+
+/* ========================================================================
+   ACCESSIBILITY - REDUCED MOTION
    ======================================================================== */
 
 @media (prefers-reduced-motion: reduce) {
-  .cv-page-content-wrapper.htmx-swapping::before {
+  .skeleton {
     animation: none;
     background: #e8e8e8;
   }
 
-  .cv-page-content-wrapper {
+  .component-wrapper .actual-content,
-    transition: none !important;
+  .component-wrapper .skeleton-content {
+    transition: none;
   }
 }
+
+/* ========================================================================
+   PRINT STYLES
+   ======================================================================== */
+
+@media print {
+  .skeleton-content {
+    display: none !important;
+  }
+
+  .component-wrapper .actual-content {
+    opacity: 1 !important;
+  }
+}
+
+/* ========================================================================
+   PERFORMANCE OPTIMIZATIONS
+   ======================================================================== */
+
+/* Force GPU acceleration for skeleton elements */
+.skeleton {
+  transform: translateZ(0);
+  backface-visibility: hidden;
+}
+
+/* Contain layout/paint/style to prevent reflow */
+.component-wrapper {
+  contain: layout style;
+}
+
+/* Optimize skeleton rendering */
+.skeleton-content {
+  contain: layout paint;
+}

templates/partials/navigation/language-selector.html

@@ -28,11 +28,12 @@
                 hx-push-url="/?lang=en"
                 aria-label="English"
                 _="on htmx:beforeRequest
-                     add .htmx-swapping to #cv-inner-content-page-1
+                     add .loading to .component-wrapper in #cv-inner-content-page-1
-                     add .htmx-swapping to #cv-inner-content-page-2
+                     add .loading to .component-wrapper in #cv-inner-content-page-2
                    on htmx:afterSwap
-                     remove .htmx-swapping from #cv-inner-content-page-1
+                     wait 100ms
-                     remove .htmx-swapping from #cv-inner-content-page-2">
+                     remove .loading from .component-wrapper in #cv-inner-content-page-1
+                     remove .loading from .component-wrapper in #cv-inner-content-page-2">
             <span>English</span>
         </button>
         <button class="selector-btn {{if eq .Lang "es"}}active{{end}}"
@@ -44,11 +45,12 @@
                 hx-push-url="/?lang=es"
                 aria-label="Español"
                 _="on htmx:beforeRequest
-                     add .htmx-swapping to #cv-inner-content-page-1
+                     add .loading to .component-wrapper in #cv-inner-content-page-1
-                     add .htmx-swapping to #cv-inner-content-page-2
+                     add .loading to .component-wrapper in #cv-inner-content-page-2
                    on htmx:afterSwap
-                     remove .htmx-swapping from #cv-inner-content-page-1
+                     wait 100ms
-                     remove .htmx-swapping from #cv-inner-content-page-2">
+                     remove .loading from .component-wrapper in #cv-inner-content-page-1
+                     remove .loading from .component-wrapper in #cv-inner-content-page-2">
             <span>Español</span>
         </button>
     </div>

templates/partials/sections/header.html

@@ -1,18 +1,33 @@
 {{define "section-header"}}
 <!-- Header with Name and Photo -->
-<div class="cv-header">
+<div class="cv-header component-wrapper">
-    <div class="cv-header-content">
+    <!-- Actual Content -->
-        <div class="cv-header-left">
+    <div class="actual-content">
-            <h1 class="cv-name">Moreno Rubio, Juan Andrés</h1>
+        <div class="cv-header-content">
-            <p class="years-experience">{{.YearsOfExperience}} {{if eq .Lang "es"}}años de experiencia{{else}}years of experience{{end}}</p>
+            <div class="cv-header-left">
+                <h1 class="cv-name">Moreno Rubio, Juan Andrés</h1>
+                <p class="years-experience">{{.YearsOfExperience}} {{if eq .Lang "es"}}años de experiencia{{else}}years of experience{{end}}</p>
 
-            <!-- Photo positioned for mobile (centered between name and intro) -->
+                <!-- Photo positioned for mobile (centered between name and intro) -->
-            <div class="cv-photo">
+                <div class="cv-photo">
-                <img src="/static/images/profile/dni.jpeg" alt="{{.CV.Personal.Name}}" onerror="this.src='/static/images/profile/placeholder.svg'">
+                    <img src="/static/images/profile/dni.jpeg" alt="{{.CV.Personal.Name}}" onerror="this.src='/static/images/profile/placeholder.svg'">
+                </div>
+
+                <!-- Intro/Excerpt Text - No section heading, just the text -->
+                <div class="intro-text">{{.CV.Summary}}</div>
             </div>
+        </div>
+    </div>
 
-            <!-- Intro/Excerpt Text - No section heading, just the text -->
+    <!-- Skeleton Content -->
-            <div class="intro-text">{{.CV.Summary}}</div>
+    <div class="skeleton-content">
+        <div class="skeleton-header">
+            <div class="skeleton-header-text">
+                <div class="skeleton skeleton-name"></div>
+                <div class="skeleton skeleton-experience-years"></div>
+                <div class="skeleton skeleton-intro"></div>
+            </div>
+            <div class="skeleton skeleton-photo"></div>
         </div>
     </div>
 </div>