Do some refactoring

frontend/src/pages/admin/AdminRelayEdit.tsx

@@ -1,9 +1,12 @@
-import { A, useNavigate, useParams } from "@solidjs/router"
+import { useNavigate, useParams } from "@solidjs/router"
 import { Show, createEffect, createResource, createSignal } from "solid-js"
 import { adminGetRelay, adminUpdateRelay } from "../../lib/api"
 import RelayForm from "../../components/RelayForm"
 import { RELAY_PLAN_IDS, type RelayPlanId } from "../../lib/relayPlans"
 import { slugify } from "../../lib/slugify"
+import BackLink from "../../components/BackLink"
+import PageContainer from "../../components/PageContainer"
+import ResourceState from "../../components/ResourceState"
 
 export default function AdminRelayEdit() {
   const navigate = useNavigate()
@@ -50,18 +53,16 @@ export default function AdminRelayEdit() {
   }
 
   return (
-    <div class="max-w-2xl mx-auto px-4 py-8">
-      <div class="flex items-center gap-2 mb-6">
-        <A href={`/admin/relays/${params.id}`} class="text-gray-500 hover:text-gray-700">← Back</A>
-      </div>
+    <PageContainer size="narrow">
+      <BackLink href={`/admin/relays/${params.id}`} label="Back" />
       <h1 class="text-2xl font-bold text-gray-900 mb-6">Edit Relay (Admin)</h1>
 
-      <Show when={relay.loading}>
-        <p class="text-gray-500">Loading relay...</p>
-      </Show>
-      <Show when={relay.error && !relay.loading}>
-        <p class="text-red-600">Failed to load relay.</p>
-      </Show>
+      <ResourceState
+        loading={relay.loading}
+        error={relay.error}
+        loadingText="Loading relay..."
+        errorText="Failed to load relay."
+      />
 
       <Show when={relay() && !relay.loading}>
         <RelayForm
@@ -83,6 +84,6 @@ export default function AdminRelayEdit() {
           submittingLabel="Saving..."
         />
       </Show>
-    </div>
+    </PageContainer>
   )
 }