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/messages/en.json

@@ -10,7 +10,9 @@
     "settings": "Settings",
     "search": "Search",
     "unknownError": "Something went wrong. Please try again.",
-    "loadFailed": "Load failed"
+    "loadFailed": "Load failed",
+    "previousPage": "Previous page",
+    "nextPage": "Next page"
   },
   "layout": {
     "nav": {
@@ -94,7 +96,9 @@
     "empty": {
       "noData": "No data",
       "noContent": "No records found"
-    }
+    },
+    "toggleSidebar": "Toggle sidebar",
+    "mainNavigation": "Main navigation"
   },
   "auth": {
     "login": {
@@ -1243,7 +1247,8 @@
         "noActiveUsersData": "No active user data",
         "unknown": "Unknown",
         "noNickname": "(no nickname)",
-        "requests": "requests"
+        "requests": "requests",
+        "refresh": "Refresh"
       },
       "appLogs": {
         "loading": "Loading...",