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

internal/db/sqlite/setup.sql

@@ -21,6 +21,59 @@ CREATE TABLE IF NOT EXISTS content_versions (
     created_by TEXT DEFAULT 'system' NOT NULL
 );
 
+-- name: InitializeCollectionsTable :exec
+CREATE TABLE IF NOT EXISTS collections (
+    id TEXT NOT NULL,
+    site_id TEXT NOT NULL,
+    container_html TEXT NOT NULL,
+    created_at INTEGER DEFAULT (strftime('%s', 'now')) NOT NULL,
+    updated_at INTEGER DEFAULT (strftime('%s', 'now')) NOT NULL,
+    last_edited_by TEXT DEFAULT 'system' NOT NULL,
+    PRIMARY KEY (id, site_id)
+);
+
+-- name: InitializeCollectionTemplatesTable :exec
+CREATE TABLE IF NOT EXISTS collection_templates (
+    template_id INTEGER PRIMARY KEY AUTOINCREMENT,
+    collection_id TEXT NOT NULL,
+    site_id TEXT NOT NULL,
+    name TEXT NOT NULL,
+    html_template TEXT NOT NULL,
+    is_default INTEGER DEFAULT 0 NOT NULL,
+    created_at INTEGER DEFAULT (strftime('%s', 'now')) NOT NULL,
+    FOREIGN KEY (collection_id, site_id) REFERENCES collections(id, site_id) ON DELETE CASCADE
+);
+
+-- name: InitializeCollectionItemsTable :exec
+CREATE TABLE IF NOT EXISTS collection_items (
+    item_id TEXT NOT NULL,
+    collection_id TEXT NOT NULL,
+    site_id TEXT NOT NULL,
+    template_id INTEGER NOT NULL,
+    html_content TEXT NOT NULL,
+    position INTEGER NOT NULL,
+    created_at INTEGER DEFAULT (strftime('%s', 'now')) NOT NULL,
+    updated_at INTEGER DEFAULT (strftime('%s', 'now')) NOT NULL,
+    last_edited_by TEXT DEFAULT 'system' NOT NULL,
+    PRIMARY KEY (item_id, collection_id, site_id),
+    FOREIGN KEY (collection_id, site_id) REFERENCES collections(id, site_id) ON DELETE CASCADE,
+    FOREIGN KEY (template_id) REFERENCES collection_templates(template_id) ON DELETE RESTRICT
+);
+
+-- name: InitializeCollectionItemVersionsTable :exec
+CREATE TABLE IF NOT EXISTS collection_item_versions (
+    version_id INTEGER PRIMARY KEY AUTOINCREMENT,
+    item_id TEXT NOT NULL,
+    collection_id TEXT NOT NULL,
+    site_id TEXT NOT NULL,
+    html_content TEXT NOT NULL,
+    template_id INTEGER NOT NULL,
+    position INTEGER NOT NULL,
+    created_at INTEGER DEFAULT (strftime('%s', 'now')) NOT NULL,
+    created_by TEXT DEFAULT 'system' NOT NULL,
+    FOREIGN KEY (item_id, collection_id, site_id) REFERENCES collection_items(item_id, collection_id, site_id) ON DELETE CASCADE
+);
+
 -- name: CreateContentSiteIndex :exec
 CREATE INDEX IF NOT EXISTS idx_content_site_id ON content(site_id);
 
@@ -30,10 +83,52 @@ CREATE INDEX IF NOT EXISTS idx_content_updated_at ON content(updated_at);
 -- name: CreateVersionsLookupIndex :exec
 CREATE INDEX IF NOT EXISTS idx_content_versions_lookup ON content_versions(content_id, site_id, created_at DESC);
 
+-- name: CreateCollectionsSiteIndex :exec
+CREATE INDEX IF NOT EXISTS idx_collections_site_id ON collections(site_id);
+
+-- name: CreateCollectionsUpdatedAtIndex :exec
+CREATE INDEX IF NOT EXISTS idx_collections_updated_at ON collections(updated_at);
+
+-- name: CreateCollectionTemplatesLookupIndex :exec
+CREATE INDEX IF NOT EXISTS idx_collection_templates_lookup ON collection_templates(collection_id, site_id);
+
+-- name: CreateCollectionTemplatesDefaultIndex :exec
+CREATE INDEX IF NOT EXISTS idx_collection_templates_default ON collection_templates(collection_id, site_id, is_default DESC);
+
+-- name: CreateCollectionItemsLookupIndex :exec
+CREATE INDEX IF NOT EXISTS idx_collection_items_lookup ON collection_items(collection_id, site_id, position);
+
+-- name: CreateCollectionItemsTemplateIndex :exec
+CREATE INDEX IF NOT EXISTS idx_collection_items_template ON collection_items(template_id);
+
+-- name: CreateCollectionItemVersionsLookupIndex :exec
+CREATE INDEX IF NOT EXISTS idx_collection_item_versions_lookup ON collection_item_versions(item_id, collection_id, site_id, created_at DESC);
+
+-- name: CreateCollectionTemplatesOneDefaultIndex :exec
+CREATE UNIQUE INDEX IF NOT EXISTS idx_collection_templates_one_default 
+ON collection_templates(collection_id, site_id) 
+WHERE is_default = 1;
+
 -- name: CreateUpdateTrigger :exec
 CREATE TRIGGER IF NOT EXISTS update_content_updated_at
 AFTER UPDATE ON content
 FOR EACH ROW
 BEGIN
     UPDATE content SET updated_at = strftime('%s', 'now') WHERE id = NEW.id AND site_id = NEW.site_id;
+END;
+
+-- name: CreateCollectionsUpdateTrigger :exec
+CREATE TRIGGER IF NOT EXISTS update_collections_updated_at
+AFTER UPDATE ON collections
+FOR EACH ROW
+BEGIN
+    UPDATE collections SET updated_at = strftime('%s', 'now') WHERE id = NEW.id AND site_id = NEW.site_id;
+END;
+
+-- name: CreateCollectionItemsUpdateTrigger :exec
+CREATE TRIGGER IF NOT EXISTS update_collection_items_updated_at
+AFTER UPDATE ON collection_items
+FOR EACH ROW
+BEGIN
+    UPDATE collection_items SET updated_at = strftime('%s', 'now') WHERE item_id = NEW.item_id AND collection_id = NEW.collection_id AND site_id = NEW.site_id;
 END;