Fix guide deep links, code block styling

- Move heading IDs from hidden permalink anchors to parent headings so deep links scroll correctly (admin.php)
- Change code block background from dark to light gray (guide.php)
- Add pre/code CSS to frontend layout.mustache for visible code blocks

cms/templates/layout.mustache

@@ -379,6 +379,30 @@
             }
         }
         
+        /* Code block styling */
+        pre {
+            background: #f8f9fa;
+            padding: 1rem;
+            border-radius: 6px;
+            overflow-x: auto;
+            border: 1px solid #dee2e6;
+            margin-bottom: 1rem;
+        }
+        pre code {
+            background: none;
+            padding: 0;
+            color: #333;
+            font-size: 0.85rem;
+            line-height: 1.5;
+        }
+        code {
+            background: #e8e8e8;
+            padding: 0.15rem 0.4rem;
+            border-radius: 3px;
+            font-size: 0.9em;
+            color: #d63384;
+        }
+
         /* Footer icon hover effects */
         .footer-icon {
             color: #6c757d;