feat(ext/vault): wire renderSettings / teardownSettings from settings component

extension/src/popup/components/settings.ts

@@ -189,3 +189,8 @@ async function renderDisplaySection(): Promise<void> {
     updateSwatch(swatch, DEFAULT_DIGIT_COLOR, DEFAULT_SYMBOL_COLOR);
   });
 }
+
+// DEV-B interface contract stub — will be replaced with real teardown logic at merge time
+export function teardownSettings(): void {
+  // no-op stub
+}