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>

events/bp/fragments/python_handlers.py

@@ -0,0 +1,58 @@
+"""Python fragment handlers for events.
+
+These handlers call domain services and use sx_call() for rendering,
+so they can't be expressed as declarative .sx handlers.
+"""
+
+from __future__ import annotations
+
+from quart import g, request
+
+from shared.services.registry import services
+
+
+async def container_cards_handler():
+    """Container-cards fragment: entries for blog listing cards.
+
+    Returns text/html with <!-- card-widget:POST_ID --> comment markers
+    so the blog consumer can split per-post fragments.
+    """
+    from sx.sx_components import render_fragment_container_cards
+
+    post_ids_raw = request.args.get("post_ids", "")
+    post_slugs_raw = request.args.get("post_slugs", "")
+    post_ids = [int(x) for x in post_ids_raw.split(",") if x.strip()]
+    post_slugs = [x.strip() for x in post_slugs_raw.split(",") if x.strip()]
+    if not post_ids:
+        return ""
+
+    slug_map = {}
+    for i, pid in enumerate(post_ids):
+        slug_map[pid] = post_slugs[i] if i < len(post_slugs) else ""
+
+    batch = await services.calendar.confirmed_entries_for_posts(g.s, post_ids)
+    return render_fragment_container_cards(batch, post_ids, slug_map)
+
+
+async def account_page_handler():
+    """Account-page fragment: tickets or bookings panel.
+
+    Returns text/sx — the account app embeds this as sx source.
+    """
+    from sx.sx_components import (
+        render_fragment_account_tickets,
+        render_fragment_account_bookings,
+    )
+
+    slug = request.args.get("slug", "")
+    user_id = request.args.get("user_id", type=int)
+    if not user_id:
+        return ""
+
+    if slug == "tickets":
+        tickets = await services.calendar.user_tickets(g.s, user_id=user_id)
+        return render_fragment_account_tickets(tickets)
+    elif slug == "bookings":
+        bookings = await services.calendar.user_bookings(g.s, user_id=user_id)
+        return render_fragment_account_bookings(bookings)
+    return ""