Auto-mount fragment handlers: eliminate fragment blueprint boilerplate across all 8 services

Fragment read API is now fully declarative — every handler is a defhandler
s-expression dispatched through one shared auto_mount_fragment_handlers()
function. Replaces 8 near-identical blueprint files (~35 lines each) with
a single function call per service. Events Python handlers (container-cards,
account-page) extracted to a standalone module.

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

cart/app.py

@@ -17,7 +17,6 @@ from bp import (
     register_page_cart,
     register_cart_global,
     register_page_admin,
-    register_fragments,
     register_actions,
     register_data,
     register_inbox,
@@ -141,7 +140,9 @@ def create_app() -> "Quart":
     app.jinja_env.globals["cart_quantity_url"] = lambda product_id: f"/quantity/{product_id}/"
     app.jinja_env.globals["cart_delete_url"] = lambda product_id: f"/delete/{product_id}/"
 
-    app.register_blueprint(register_fragments())
+    from shared.sx.handlers import auto_mount_fragment_handlers
+    auto_mount_fragment_handlers(app, "cart")
+
     app.register_blueprint(register_actions())
     app.register_blueprint(register_data())
     app.register_blueprint(register_inbox())

cart/bp/__init__.py

@@ -2,7 +2,6 @@ from .cart.overview_routes import register as register_cart_overview
 from .cart.page_routes import register as register_page_cart
 from .cart.global_routes import register as register_cart_global
 from .page_admin.routes import register as register_page_admin
-from .fragments import register_fragments
 from .actions import register_actions
 from .data import register_data
 from .inbox import register_inbox

cart/bp/fragments/__init__.py

@@ -1 +0,0 @@
-from .routes import register as register_fragments

cart/bp/fragments/routes.py

@@ -1,36 +0,0 @@
-"""Cart app fragment endpoints.
-
-Exposes sx fragments at ``/internal/fragments/<type>`` for consumption
-by other coop apps via the fragment client.
-
-All handlers are defined declaratively in .sx files under
-``cart/sx/handlers/`` and dispatched via the sx handler registry.
-"""
-
-from __future__ import annotations
-
-from quart import Blueprint, Response, request
-
-from shared.infrastructure.fragments import FRAGMENT_HEADER
-from shared.sx.handlers import get_handler, execute_handler
-
-
-def register():
-    bp = Blueprint("fragments", __name__, url_prefix="/internal/fragments")
-
-    @bp.before_request
-    async def _require_fragment_header():
-        if not request.headers.get(FRAGMENT_HEADER):
-            return Response("", status=403)
-
-    @bp.get("/<fragment_type>")
-    async def get_fragment(fragment_type: str):
-        handler_def = get_handler("cart", fragment_type)
-        if handler_def is not None:
-            result = await execute_handler(
-                handler_def, "cart", args=dict(request.args),
-            )
-            return Response(result, status=200, content_type="text/sx")
-        return Response("", status=200, content_type="text/sx")
-
-    return bp