Refactor SX templates: shared components, Python migration, cleanup

- Extract shared components (empty-state, delete-btn, sentinel, crud-*,
  view-toggle, img-or-placeholder, avatar, sumup-settings-form, auth
  forms, order tables/detail/checkout)
- Migrate all Python sx_call() callers to use shared components directly
- Remove 55+ thin wrapper defcomps from domain .sx files
- Remove trivial passthrough wrappers (blog-header-label, market-card-text, etc)
- Unify duplicate auth flows (account + federation) into shared/sx/templates/auth.sx
- Unify duplicate order views (cart + orders) into shared/sx/templates/orders.sx
- Disable static file caching in dev (SEND_FILE_MAX_AGE_DEFAULT=0)
- Add SX response validation and debug headers

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

events/bp/fragments/routes.py

@@ -50,9 +50,11 @@ def register():
         page = int(request.args.get("page", 1))
         exclude = request.args.get("exclude", "")
         excludes = [e.strip() for e in exclude.split(",") if e.strip()]
+        current_calendar = request.args.get("current_calendar", "")
 
         styles = current_app.jinja_env.globals.get("styles", {})
-        nav_class = styles.get("nav_button_less_pad", "")
+        nav_class = styles.get("nav_button", "")
+        select_colours = current_app.jinja_env.globals.get("select_colours", "")
         parts = []
 
         # Calendar entries nav
@@ -87,8 +89,10 @@ def register():
             )
             for cal in calendars:
                 href = events_url(f"/{post_slug}/{cal.slug}/")
+                is_selected = (cal.slug == current_calendar) if current_calendar else False
                 parts.append(sx_call("calendar-link-nav",
-                    href=href, name=cal.name, nav_class=nav_class))
+                    href=href, name=cal.name, nav_class=nav_class,
+                    is_selected=is_selected, select_colours=select_colours))
 
         if not parts:
             return ""