Enable cross-subdomain htmx and purify layout to sexp

- Disable htmx selfRequestsOnly, add CORS headers for *.rose-ash.com
- Remove same-origin guards from ~menu-row and ~nav-link htmx attrs
- Convert ~app-layout from string-concatenated HTML to pure sexp tree
- Extract ~app-head component, replace ~app-shell with inline structure
- Convert hamburger SVG from Python HTML constant to ~hamburger sexp component
- Fix cross-domain fragment URLs (events_url, market_url)
- Fix starts-with? primitive to handle nil values
- Fix duplicate admin menu rows on OOB swaps
- Add calendar admin nav links (slots, description)
- Convert slots page from Jinja to sexp rendering
- Disable page caching in development mode
- Backfill migration to clean orphaned container_relations

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

events/bp/slots/routes.py

@@ -44,16 +44,14 @@ def register():
 
     @bp.get("/")
     async def get(**kwargs):
+        from shared.sexp.page import get_template_context
+        from sexp.sexp_components import render_slots_page, render_slots_oob
+
+        tctx = await get_template_context()
         if not is_htmx_request():
-          # Normal browser request: full page with layout
-          html = await render_template(
-            "_types/slots/index.html",
-            )
+            html = await render_slots_page(tctx)
         else:
-            
-            html = await render_template(
-              "_types/slots/_oob_elements.html",
-            )
+            html = await render_slots_oob(tctx)
         return await make_response(html)