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>

app.py

@@ -19,9 +19,9 @@ from bp import (
 )
 
 
-async def coop_context() -> dict:
+async def blog_context() -> dict:
     """
-    Coop app context processor.
+    Blog app context processor.
 
     - menu_items: via shared.services.navigation
     - cart_count/cart_total: via cart service (shared DB)
@@ -50,8 +50,8 @@ def create_app() -> "Quart":
     from services import register_domain_services
 
     app = create_base_app(
-        "coop",
-        context_fn=coop_context,
+        "blog",
+        context_fn=blog_context,
         domain_services_fn=register_domain_services,
     )