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>

federation/bp/auth/routes.py

@@ -11,7 +11,6 @@ from datetime import datetime, timezone, timedelta
 from quart import (
     Blueprint,
     request,
-    render_template,
     redirect,
     url_for,
     session as qsession,
@@ -101,7 +100,7 @@ def register(url_prefix="/auth"):
             redirect_url = pop_login_redirect_target()
             return redirect(redirect_url)
         from shared.sexp.page import get_template_context
-        from sexp_components import render_login_page
+        from sexp.sexp_components import render_login_page
         ctx = await get_template_context()
         return await render_login_page(ctx)
 
@@ -112,14 +111,10 @@ def register(url_prefix="/auth"):
 
         is_valid, email = validate_email(email_input)
         if not is_valid:
-            return (
-                await render_template(
-                    "auth/login.html",
-                    error="Please enter a valid email address.",
-                    email=email_input,
-                ),
-                400,
-            )
+            from shared.sexp.page import get_template_context
+            from sexp.sexp_components import render_login_page
+            ctx = await get_template_context(error="Please enter a valid email address.", email=email_input)
+            return await render_login_page(ctx), 400
 
         user = await find_or_create_user(g.s, email)
         token, expires = await create_magic_link(g.s, user.id)
@@ -137,11 +132,10 @@ def register(url_prefix="/auth"):
                 "Please try again in a moment."
             )
 
-        return await render_template(
-            "auth/check_email.html",
-            email=email,
-            email_error=email_error,
-        )
+        from shared.sexp.page import get_template_context
+        from sexp.sexp_components import render_check_email_page
+        ctx = await get_template_context(email=email, email_error=email_error)
+        return await render_check_email_page(ctx)
 
     @auth_bp.get("/magic/<token>/")
     async def magic(token: str):
@@ -154,20 +148,17 @@ def register(url_prefix="/auth"):
                     user, error = await validate_magic_link(s, token)
 
                     if error:
-                        return (
-                            await render_template("auth/login.html", error=error),
-                            400,
-                        )
+                        from shared.sexp.page import get_template_context
+                        from sexp.sexp_components import render_login_page
+                        ctx = await get_template_context(error=error)
+                        return await render_login_page(ctx), 400
                     user_id = user.id
 
         except Exception:
-            return (
-                await render_template(
-                    "auth/login.html",
-                    error="Could not sign you in right now. Please try again.",
-                ),
-                502,
-            )
+            from shared.sexp.page import get_template_context
+            from sexp.sexp_components import render_login_page
+            ctx = await get_template_context(error="Could not sign you in right now. Please try again.")
+            return await render_login_page(ctx), 502
 
         assert user_id is not None