fix(pos): corregir enlaces de navegacion en todas las paginas

Reemplaza enlaces del design system (dashboard.html, pos.html, etc.)
con rutas reales del POS (/pos/dashboard, /pos/sale, etc.).
Limpia archivos backup.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pos/templates/dashboard.html

@@ -1286,7 +1286,7 @@
 
         <div class="sidebar__section-label">Principal</div>
 
-        <a href="dashboard.html" class="nav-link active">
+        <a href="/pos/dashboard" class="nav-link active">
           <span class="nav-link__icon">
             <svg width="16" height="16" viewBox="0 0 16 16" fill="none">
               <rect x="1" y="1" width="6" height="6" rx="1" fill="currentColor" opacity="0.9"/>
@@ -1298,7 +1298,7 @@
           Dashboard
         </a>
 
-        <a href="pos.html" class="nav-link">
+        <a href="/pos/sale" class="nav-link">
           <span class="nav-link__icon">
             <svg width="16" height="16" viewBox="0 0 16 16" fill="none">
               <rect x="1" y="2" width="14" height="10" rx="1.5" stroke="currentColor" stroke-width="1.5"/>
@@ -1310,7 +1310,7 @@
           POS
         </a>
 
-        <a href="catalogo.html" class="nav-link">
+        <a href="/pos/catalog" class="nav-link">
           <span class="nav-link__icon">
             <svg width="16" height="16" viewBox="0 0 16 16" fill="none">
               <path d="M3 2h7l3 3v9H3V2z" stroke="currentColor" stroke-width="1.5" stroke-linejoin="round"/>