fix(operator,portal): env-driven sign-out URLs + host labels (no more .local in prod)

Operator sign-out hardcoded the dev Authentik end-session URL, so prod
logout landed on auth.dezky.local. Mirror the portal's env-driven pattern
(NUXT_PUBLIC_AUTH_URL/NUXT_PUBLIC_OPERATOR_URL with .local fallbacks).
Expose authUrl/operatorUrl via public runtimeConfig and use them for the
Authentik admin links and the cosmetic host labels (sidebar, eyebrows,
auth-page hints). Portal: signed-out + webmail copy now derive their hosts
from runtime config (new public.mailUrl, NUXT_PUBLIC_MAIL_URL in prod).

apps/portal/pages/signed-out.vue

@@ -1,4 +1,5 @@
 <script setup lang="ts">
+const portalHost = new URL(useRuntimeConfig().public.portalUrl as string).host
 // Sign-out landing. /api/auth/sign-out cleared the local session and bounced
 // through Authentik's end-session endpoint, which ended the IdP session.
 // At this point the user has no portal session and no Authentik session —
@@ -30,7 +31,7 @@ function signInAgain() {
 
     <AuthFooterLink>
       Closing the tab? Your data stays put on
-      <span class="mono">app.dezky.local</span>.
+      <span class="mono">{{ portalHost }}</span>.
     </AuthFooterLink>
   </AuthShell>
 </template>