feat(dashboard): cards colapsables en Analytics Dashboard

- Convertir 9 cards a estructura colapsable con Bootstrap 5 Collapse
- Headers fuera de cards como botones clickeables
- Cards contraídos por defecto para reducir scroll
- Añadir animación de rotación del chevron (180°)
- Ajustar selector JS de loading overlay a .collapsible-section
- CSS para estados hover, focus y bordes redondeados

Cards modificados:
1. CTR 0% (collapse-ctr-zero)
2. Quick Wins (collapse-quick-wins)
3. Contenido Decadencia (collapse-decay)
4. Contenido Estrella (collapse-star)
5. Infraposicionados (collapse-infrapos)
6. Click Distribution (collapse-click-dist)
7. Top Búsquedas (collapse-top-searches)
8. Top Clicks (collapse-top-clicks)
9. Sin Resultados (collapse-zero-results)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

admin/assets/dashboard.js

@@ -99,10 +99,10 @@
             return;
         }
 
-        // Find the card container and add loading state (keeps size, shows overlay)
-        var card = tbody.closest('.card');
-        if (card) {
-            card.classList.add('is-loading-table');
+        // Find the collapsible section container and add loading state (keeps size, shows overlay)
+        var section = tbody.closest('.collapsible-section');
+        if (section) {
+            section.classList.add('is-loading-table');
         }
 
         // Build form data
@@ -157,8 +157,8 @@
                 tbody.innerHTML = html;
 
                 // Remove loading state
-                if (card) {
-                    card.classList.remove('is-loading-table');
+                if (section) {
+                    section.classList.remove('is-loading-table');
                 }
 
                 // Update pagination
@@ -167,16 +167,16 @@
                     bindPaginationEvents(paginationDiv, tableId);
                 }
             } else {
-                if (card) {
-                    card.classList.remove('is-loading-table');
+                if (section) {
+                    section.classList.remove('is-loading-table');
                 }
                 showErrorMessage('Error al cargar datos');
                 console.error('AJAX error:', result);
             }
         })
         .catch(function(error) {
-            if (card) {
-                card.classList.remove('is-loading-table');
+            if (section) {
+                section.classList.remove('is-loading-table');
             }
             console.error('Fetch error:', error);
             showErrorMessage('Error de conexión');