Phase 7: Replace render_template() with s-expression rendering in all POST/PUT/DELETE routes

Eliminates all render_template() calls from POST/PUT/DELETE handlers across
all 7 services. Moves sexp_components.py into sexp/ packages per service.

- Blog: like toggle, snippets, cache clear, features/sumup/entry panels,
  create/delete market, WYSIWYG editor panel (render_editor_panel)
- Federation: like/unlike/boost/unboost, follow/unfollow, actor card,
  interaction buttons
- Events: ticket widget, checkin, confirm/decline/provisional, tickets
  config, posts CRUD, description edit/save, calendar/slot/ticket_type
  CRUD, payments, buy tickets, day main panel, entry page
- Market: like toggle, cart add response
- Account: newsletter toggle
- Cart: checkout error pages (3 handlers)
- Orders: checkout error page (1 handler)

Remaining render_template() calls are exclusively in GET handlers and
internal services (email templates, fragment endpoints).

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

events/bp/all_events/routes.py

@@ -66,7 +66,7 @@ def register() -> Blueprint:
         entries, has_more, pending_tickets, page_info = await _load_entries(page)
 
         from shared.sexp.page import get_template_context
-        from sexp_components import render_all_events_page, render_all_events_oob
+        from sexp.sexp_components import render_all_events_page, render_all_events_oob
 
         ctx = await get_template_context()
         if is_htmx_request():
@@ -83,7 +83,7 @@ def register() -> Blueprint:
 
         entries, has_more, pending_tickets, page_info = await _load_entries(page)
 
-        from sexp_components import render_all_events_cards
+        from sexp.sexp_components import render_all_events_cards
         html = await render_all_events_cards(entries, has_more, pending_tickets, page_info, page, view)
         return await make_response(html, 200)
 
@@ -124,12 +124,8 @@ def register() -> Blueprint:
         if ident["session_id"] is not None:
             frag_params["session_id"] = ident["session_id"]
 
-        widget_html = await render_template(
-            "_types/page_summary/_ticket_widget.html",
-            entry=entry,
-            qty=qty,
-            ticket_url="/all-tickets/adjust",
-        )
+        from sexp.sexp_components import render_ticket_widget
+        widget_html = render_ticket_widget(entry, qty, "/all-tickets/adjust")
         mini_html = await fetch_fragment("cart", "cart-mini", params=frag_params, required=False)
         return await make_response(widget_html + mini_html, 200)