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/inventory.html

@@ -1228,7 +1228,7 @@
       <nav class="sidebar__nav">
         <div class="nav-section-label">Principal</div>
 
-        <a class="nav-item" href="pos.html">
+        <a class="nav-item" href="/pos/sale">
           <!-- Dashboard icon -->
           <svg class="nav-item__icon" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.75" stroke-linecap="round" stroke-linejoin="round">
             <rect x="3" y="3" width="7" height="7"/><rect x="14" y="3" width="7" height="7"/>
@@ -1237,14 +1237,14 @@
           <span>Dashboard</span>
         </a>
 
-        <a class="nav-item" href="pos.html">
+        <a class="nav-item" href="/pos/sale">
           <svg class="nav-item__icon" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.75" stroke-linecap="round" stroke-linejoin="round">
             <rect x="2" y="3" width="20" height="14" rx="2"/><path d="M8 21h8M12 17v4"/>
           </svg>
           <span>POS</span>
         </a>
 
-        <a class="nav-item" href="catalogo.html">
+        <a class="nav-item" href="/pos/catalog">
           <svg class="nav-item__icon" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.75" stroke-linecap="round" stroke-linejoin="round">
             <path d="M4 6h16M4 10h16M4 14h16M4 18h16"/>
           </svg>