Commit transaction before fetching cart-mini fragment

The cart-mini fragment is fetched via HTTP from the cart app, which
uses its own DB connection. Without committing first, the cart app
sees stale data (no new item). Commit the transaction, start a new
one so after_request can still commit cleanly.

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

bp/product/routes.py

@@ -254,6 +254,10 @@ def register():
 
         # htmx response: OOB-swap mini cart + product buttons
         if request.headers.get("HX-Request") == "true":
+            # Commit so the cart app sees the updated data when we fetch the fragment
+            await g.tx.commit()
+            g.tx = await g.s.begin()
+
             from shared.infrastructure.fragments import fetch_fragment
             from shared.infrastructure.cart_identity import current_cart_identity as _ci
             frag_ident = _ci()