Add admin panel, enhanced search, Gonher import and expand API

- Add admin interface (admin.html, admin.js) for managing catalog data
- Add enhanced search module with advanced filtering capabilities
- Expand server.py with new API endpoints and admin functionality
- Add Gonher catalog import scripts (import_gonher_catalog.py, import_gonher_complete.py)
- Add demo data population script and sample CSV data
- Update customer landing page and dashboard with UI improvements
- Update database with enriched vehicle and parts data

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

dashboard/customer-landing.html

@@ -113,6 +113,17 @@
             width: 100%;
         }
 
+        .nav-links a.admin-link {
+            color: var(--accent);
+            font-weight: 600;
+            opacity: 0.8;
+            transition: opacity 0.3s;
+        }
+
+        .nav-links a.admin-link:hover {
+            opacity: 1;
+        }
+
         .header-actions {
             display: flex;
             align-items: center;
@@ -1061,6 +1072,7 @@
             <a href="#brands-section">Marcas</a>
             <a href="#featured-section">Productos</a>
             <a href="#cta-section">Contacto</a>
+            <a href="admin.html" class="admin-link">⚡ Admin</a>
         </nav>
         <div class="header-actions">
             <button class="search-btn" onclick="openSearchModal()">🔍</button>