Implement complete collection persistence with database-backed survival across server restarts

• Add full multi-table schema for collections with normalized design (collections, collection_templates, collection_items, collection_item_versions)
• Implement collection detection and processing in enhancement pipeline for .insertr-add elements
• Add template extraction and storage from existing HTML children with multi-variant support
• Enable collection reconstruction from database on server restart with proper DOM rebuilding
• Extend ContentClient interface with collection operations and full database integration
• Update enhance command to use engine.DatabaseClient for collection persistence support

lib/src/core/editor.js

@@ -1,4 +1,5 @@
 import { InsertrFormRenderer } from '../ui/form-renderer.js';
+import { CollectionManager } from '../ui/collection-manager.js';
 
 /**
  * InsertrEditor - Content editing workflow and business logic
@@ -67,8 +68,18 @@ export class InsertrEditor {
     initializeElement(meta) {
         const { element } = meta;
         
-        // Add click handler for editing
-        this.addClickHandler(element, meta);
+        if (meta.editorType === 'collection') {
+            // Initialize collection management
+            this.initializeCollection(meta);
+        } else {
+            // Add click handler for editing individual elements
+            this.addClickHandler(element, meta);
+        }
+    }
+    
+    initializeCollection(meta) {
+        const collectionManager = new CollectionManager(meta, this.apiClient, this.auth);
+        collectionManager.initialize();
     }
     
     addClickHandler(element, meta) {

lib/src/core/insertr.js

@@ -12,17 +12,19 @@ export class InsertrCore {
 
     // Find all enhanced elements on the page
     findEnhancedElements() {
-        return document.querySelectorAll('.insertr');
+        return document.querySelectorAll('.insertr, .insertr-add');
     }
 
     // Get element metadata
     getElementMetadata(element) {
         const existingId = element.getAttribute('data-content-id');
+        const isCollection = element.classList.contains('insertr-add');
 
         return {
             contentId: existingId,
             element: element,
-            htmlMarkup: element.outerHTML // Server will generate ID from this
+            htmlMarkup: element.outerHTML, // Server will generate ID from this
+            editorType: isCollection ? 'collection' : 'element'
         };
     }