fix(auth): RP-initiated Keycloak logout + PKCE verifier race

Clicking logout previously only called supabase.auth.signOut(): Keycloak's
SSO cookie was untouched, so the (app) layout's $effect immediately
re-fired login() and Keycloak silently re-authenticated — logout looked
broken. That same chain also surfaced "PKCE code verifier not found in
storage" on prod, since signOut()'s async storage clear could race
signInWithOAuth()'s verifier write, or the $effect could double-fire and
overwrite verifiers mid-flight.

- logout(): signOut() then redirect to Keycloak's end_session endpoint
  (client_id + post_logout_redirect_uri=/logged-out). Keycloak shows a
  one-click "Do you want to log out?" confirmation because GoTrue's proxy
  flow does not expose the id_token, so we can't pass id_token_hint.
- isLoggingOut flag + guard in (app) layout $effect: prevents auto-relogin
  during the logout navigation.
- New public /logged-out route, outside the (app) group.
- A-05 rewritten, new A-07 (fresh login must prompt for credentials after
  RP-initiated logout).
- pgTAP 008 extended with 4 assertions for migration 014's UPDATE trigger.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/messages/en.json

@@ -13,6 +13,9 @@
 	"login_button": "Sign in",
 	"logout_button": "Sign out",
 	"auth_back_to_home": "Back to home",
+	"logged_out_title": "You've been signed out",
+	"logged_out_subtitle": "Sign in again to continue.",
+	"logged_out_sign_in": "Sign in",
 	"onboarding_title": "Welcome to Colectivo",
 	"onboarding_subtitle": "Get started by creating a new collective or joining an existing one.",
 	"onboarding_create_tab": "Create",

apps/web/messages/es.json

@@ -13,6 +13,9 @@
 	"login_button": "Iniciar sesión",
 	"logout_button": "Cerrar sesión",
 	"auth_back_to_home": "Volver al inicio",
+	"logged_out_title": "Sesión cerrada",
+	"logged_out_subtitle": "Inicia sesión de nuevo para continuar.",
+	"logged_out_sign_in": "Iniciar sesión",
 	"onboarding_title": "Bienvenido a Colectivo",
 	"onboarding_subtitle": "Crea un nuevo colectivo o únete a uno existente.",
 	"onboarding_create_tab": "Crear",