Drop container_relations from blog DB — now lives in cart

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

blog/alembic/env.py

@@ -6,7 +6,6 @@ MODELS = [
     "shared.models.kv",
     "shared.models.menu_item",
     "shared.models.menu_node",
-    "shared.models.container_relation",
     "blog.models.snippet",
     "blog.models.tag_group",
 ]
@@ -14,7 +13,7 @@ MODELS = [
 TABLES = frozenset({
     "posts", "authors", "post_authors", "tags", "post_tags", "post_likes",
     "snippets", "tag_groups", "tag_group_tags",
-    "menu_items", "menu_nodes", "kv", "container_relations",
+    "menu_items", "menu_nodes", "kv",
 })
 
 run_alembic(context.config, MODELS, TABLES)