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/app/(main)/admin/database/components/table-browser.tsx

@@ -140,7 +140,10 @@ export function TableBrowser({
             <Skeleton className='h-8 w-48' />
           ) : (
             <Select value={selectedTable} onValueChange={handleTableChange}>
-              <SelectTrigger className='h-8 w-[200px] text-xs bg-background border-border/40'>
+              <SelectTrigger
+                aria-label={t('selectTable')}
+                className='h-8 w-[200px] text-xs bg-background border-border/40'
+              >
                 <SelectValue placeholder={t('selectTable')} />
               </SelectTrigger>
               <SelectContent className='max-h-[300px]'>