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>

shared/sx/handlers.py

@@ -204,3 +204,42 @@ def create_handler_blueprint(service_name: str) -> Any:
     bp._python_handlers = _python_handlers  # type: ignore[attr-defined]
 
     return bp
+
+
+# ---------------------------------------------------------------------------
+# Direct app mount — replaces per-service fragment blueprint boilerplate
+# ---------------------------------------------------------------------------
+
+def auto_mount_fragment_handlers(app: Any, service_name: str) -> Callable:
+    """Mount ``/internal/fragments/<type>`` directly on the app.
+
+    Returns an ``add_handler(name, fn, content_type)`` function for
+    registering Python handler overrides (checked before SX handlers).
+    """
+    from quart import Response, request
+    from shared.infrastructure.fragments import FRAGMENT_HEADER
+
+    python_handlers: dict[str, Callable[[], Awaitable[str]]] = {}
+    html_types: set[str] = set()
+
+    @app.get("/internal/fragments/<fragment_type>")
+    async def _fragment_dispatch(fragment_type: str):
+        if not request.headers.get(FRAGMENT_HEADER):
+            return Response("", status=403)
+        py = python_handlers.get(fragment_type)
+        if py is not None:
+            result = await py()
+            ct = "text/html" if fragment_type in html_types else "text/sx"
+            return Response(result, status=200, content_type=ct)
+        hdef = get_handler(service_name, fragment_type)
+        if hdef is not None:
+            result = await execute_handler(hdef, service_name, args=dict(request.args))
+            return Response(result, status=200, content_type="text/sx")
+        return Response("", status=200, content_type="text/sx")
+
+    def add_handler(name: str, fn: Callable[[], Awaitable[str]], content_type: str = "text/sx") -> None:
+        python_handlers[name] = fn
+        if content_type == "text/html":
+            html_types.add(name)
+
+    return add_handler