Add dynamic custom field display and remove redundant admin routes

Major improvements to tenant management:
1. Dynamic field display - Product lists now automatically show all custom fields based on tenant configuration (e.g., inventory, custom attributes)
2. Fixed Jinja2 template scoping issue - Product field values now correctly display in edit forms using selectattr filter
3. Simplified URL structure - Removed redundant /tenant/admin/ routes, all product management now at /tenant/ root
4. Enhanced tenant landing page - Added delete functionality with confirmation modal, shows all custom fields except images
5. Updated all routes and redirects to use simplified paths (/tenant/add, /tenant/edit, etc.)

This consolidates the interface so /tenant/ serves as the main dashboard with full product management capabilities, while /tenant/settings handles configuration.

src/templates/admin/add_product.html

@@ -10,7 +10,7 @@
                 <h2>Add New Product</h2>
             </div>
             <div class="card-body">
-                <form action="{{ url_for('admin.add_product', tenant_id=tenant_id) }}" method="POST" enctype="multipart/form-data">
+                <form action="/{{ tenant_id }}/add" method="POST" enctype="multipart/form-data">
                     <div class="mb-3">
                         <label for="product_id" class="form-label">Product ID *</label>
                         <div class="input-group">
@@ -67,7 +67,7 @@
                     {% endif %}
                     
                     <div class="d-flex justify-content-between">
-                        <a href="{{ url_for('admin.index', tenant_id=tenant_id) }}" class="btn btn-secondary">Cancel</a>
+                        <a href="/{{ tenant_id }}/" class="btn btn-secondary">Cancel</a>
                         <button type="submit" class="btn btn-primary">Add Product</button>
                     </div>
                 </form>