Add fragment blueprint + sync shared: micro-frontend infrastructure

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

app.py

@@ -15,6 +15,7 @@ from bp import (
     register_page_cart,
     register_cart_global,
     register_orders,
+    register_fragments,
 )
 from bp.cart.services import (
     get_cart,
@@ -112,6 +113,8 @@ 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())
+
     # --- Page slug hydration (follows events/market app pattern) ---
 
     @app.url_value_preprocessor

bp/__init__.py

@@ -3,3 +3,4 @@ from .cart.page_routes import register as register_page_cart
 from .cart.global_routes import register as register_cart_global
 from .order.routes import register as register_order
 from .orders.routes import register as register_orders
+from .fragments import register_fragments

bp/fragments/__init__.py

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

bp/fragments/routes.py

@@ -0,0 +1,34 @@
+"""Cart app fragment endpoints.
+
+Exposes HTML fragments at ``/internal/fragments/<type>`` for consumption
+by other coop apps via the fragment client.
+"""
+
+from __future__ import annotations
+
+from quart import Blueprint, Response, request
+
+from shared.infrastructure.fragments import FRAGMENT_HEADER
+
+
+def register():
+    bp = Blueprint("fragments", __name__, url_prefix="/internal/fragments")
+
+    _handlers: dict[str, object] = {}
+
+    @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 = _handlers.get(fragment_type)
+        if handler is None:
+            return Response("", status=200, content_type="text/html")
+        html = await handler()
+        return Response(html, status=200, content_type="text/html")
+
+    bp._fragment_handlers = _handlers
+
+    return bp