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>

shared/browser/app/redis_cacher.py

@@ -187,7 +187,7 @@ def cache_page(
         async def wrapper(*args, **kwargs):
             r = get_redis()
 
-            if not r or request.method != "GET":
+            if not r or request.method != "GET" or current_app.config.get("NO_PAGE_CACHE"):
                 return await view(*args, **kwargs)
             uid = get_user_id()