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

internal/apps/cap/middleware.go

@@ -16,6 +16,10 @@ func VerifyMiddleware(mgr *Manager, scope string) gin.HandlerFunc {
 			c.Next()
 			return
 		}
+		if mgr == nil {
+			response.AbortUnauthorized(c, errCapTokenInvalidOrExpired)
+			return
+		}
 
 		token := c.GetHeader("X-Cap-Token")
 		if token == "" {