feat(core): sync framework security hardening and accessibility improvements

- add util.Go with panic recovery for background goroutines
- add util.EscapeLike and explicit ESCAPE clause for SQL LIKE queries
- add DummyCheckPassword and subtle.ConstantTimeCompare against timing attacks
- enforce session ID rotation upon login/oauth callback to prevent session fixation
- add sliding window login failure rate limiting and oauth state rate limiting
- fix redis client capture race in pubsub listeners and wait on stop channel
- adjust global --primary to oklch(51.1% 0.262 276.966) for WCAG AA contrast
- fix semantic heading levels and missing aria-labels across UI components
- document security, concurrency, and a11y standards in AGENTS.md

frontend/components/layout/loading.tsx

@@ -120,9 +120,7 @@ export function LoadingState({
       </div>
 
       {displayTitle && (
-        <h3 className='text-sm font-medium mb-1 animate-pulse'>
-          {displayTitle}
-        </h3>
+        <p className='text-sm font-medium mb-1 animate-pulse'>{displayTitle}</p>
       )}
 
       {displayDescription && (