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

pkg/util/like_test.go

@@ -0,0 +1,22 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package util
+
+import "testing"
+
+func TestEscapeLike(t *testing.T) {
+	cases := map[string]string{
+		"":            "",
+		"/my_page":    `/my\_page`,
+		"100%":        `100\%`,
+		`a\b`:         `a\\b`,
+		`%_\`:         `\%\_\\`,
+		"normal/path": "normal/path",
+	}
+	for input, want := range cases {
+		if got := EscapeLike(input); got != want {
+			t.Errorf("EscapeLike(%q) = %q, want %q", input, got, want)
+		}
+	}
+}