Lock down coming-soon mode to block all users including authenticated

Remove auth bypass from coming-soon middleware so no one can access
the in-development site in production. Remove unused login button
from coming-soon page since wiki has its own OIDC login flow.

app/pages/coming-soon.vue

@@ -4,13 +4,6 @@
       <h1 class="text-display-xl font-bold mb-4">Ghost Guild</h1>
       <p class="text-display-sm text-guild-400">Coming Soon</p>
     </a>
-    <button
-      class="mt-12 text-sm text-guild-500 hover:text-guild-300 transition-colors"
-      @click="openLoginModal"
-    >
-      Member login
-    </button>
-    <LoginModal />
   </div>
 </template>
 
@@ -18,6 +11,4 @@
 definePageMeta({
   layout: "coming-soon",
 });
-
-const { openLoginModal } = useLoginModal();
 </script>