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>

blog/bp/snippets/routes.py

@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-from quart import Blueprint, render_template, make_response, request, g, abort
+from quart import Blueprint, make_response, request, g, abort
 from sqlalchemy import select, or_
 from sqlalchemy.orm import selectinload
 
@@ -39,7 +39,7 @@ def register():
         is_admin = g.rights.get("admin")
 
         from shared.sexp.page import get_template_context
-        from sexp_components import render_snippets_page, render_snippets_oob
+        from sexp.sexp_components import render_snippets_page, render_snippets_oob
 
         tctx = await get_template_context()
         tctx["snippets"] = snippets
@@ -67,11 +67,8 @@ def register():
         await g.s.flush()
 
         snippets = await _visible_snippets(g.s)
-        html = await render_template(
-            "_types/snippets/_list.html",
-            snippets=snippets,
-            is_admin=is_admin,
-        )
+        from sexp.sexp_components import render_snippets_list
+        html = render_snippets_list(snippets, is_admin)
         return await make_response(html)
 
     @bp.patch("/<int:snippet_id>/visibility/")
@@ -95,11 +92,8 @@ def register():
         await g.s.flush()
 
         snippets = await _visible_snippets(g.s)
-        html = await render_template(
-            "_types/snippets/_list.html",
-            snippets=snippets,
-            is_admin=True,
-        )
+        from sexp.sexp_components import render_snippets_list
+        html = render_snippets_list(snippets, True)
         return await make_response(html)
 
     return bp