Rename coop to blog in app code and config

- App name: "coop" → "blog"
- coop_context() → blog_context()
- coop_url → blog_url imports
- app_url("coop") → app_url("blog")
- Config keys: coop_root/coop_title → market_root/market_title
- Sync shared submodule

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

services/__init__.py

@@ -1,9 +1,9 @@
-"""Blog (coop) app service registration."""
+"""Blog app service registration."""
 from __future__ import annotations
 
 
 def register_domain_services() -> None:
-    """Register services for the blog (coop) app.
+    """Register services for the blog app.
 
     Blog owns: Post, Tag, Author, PostAuthor, PostTag, PostLike.
     Standard deployment registers all 4 services as real DB impls