Add WalletConnect stub, track surfaces, legacy SPA retirement, and dual-domain checks.

Publish walletconnect config endpoints, Track 3/4 notes on analytics/operator pages, legacy SPA at /legacy/index.html with root redirect, and a parity verifier for explorer.d-bis.org vs blockscout.defi-oracle.io.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/components/explorer/OperationsPageShell.tsx

@@ -3,6 +3,7 @@ import { Card } from '@/libs/frontend-ui-primitives'
 import type { ExplorerFeaturePage } from '@/data/explorerOperations'
 import OperationsSurfaceNav from './OperationsSurfaceNav'
 import OperationsActionGrid from './OperationsActionGrid'
+import OperationsTrackNote from './OperationsTrackNote'
 
 export type StatusTone = 'normal' | 'warning' | 'danger'
 
@@ -108,6 +109,10 @@ export default function OperationsPageShell({
         </Card>
       ) : null}
 
+      {page.accessTrack && page.accessNote ? (
+        <OperationsTrackNote track={page.accessTrack} note={page.accessNote} />
+      ) : null}
+
       <OperationsSurfaceNav />
 
       {children}

frontend/src/components/explorer/OperationsTrackNote.tsx

@@ -0,0 +1,20 @@
+import { Card } from '@/libs/frontend-ui-primitives'
+
+export default function OperationsTrackNote({
+  track,
+  note,
+  className,
+}: {
+  track: number
+  note: string
+  className?: string
+}) {
+  return (
+    <Card className={className ?? 'mb-6 border border-violet-200 bg-violet-50/70 dark:border-violet-900/50 dark:bg-violet-950/20'}>
+      <div className="text-xs font-semibold uppercase tracking-[0.2em] text-violet-700 dark:text-violet-200">
+        Track {track} public surface
+      </div>
+      <p className="mt-2 text-sm leading-6 text-violet-950 dark:text-violet-100">{note}</p>
+    </Card>
+  )
+}