Decoupling audit: remove coop_api, fix blog admin calendar imports

- Delete coop_api.py (dead internal API endpoint)
- Replace cross-app calendar imports with shared service calls
- Update shared submodule

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

bp/__init__.py

@@ -3,4 +3,3 @@ from .blog.routes import register as register_blog_bp
 from .admin.routes import register as register_admin
 from .menu_items.routes import register as register_menu_items
 from .snippets.routes import register as register_snippets
-from .coop_api import register as register_coop_api