fix(ui): reliable federation-join feedback (90s timeout + re-check + success)

Joining a Fedimint federation is heavy and routinely outlasts the default 15s
client timeout while still succeeding server-side, so the UI wrongly showed
failure. Bump the join timeout to 90s, and on any error re-check the list: if a
new federation appeared the join worked — show 'Federation joined.' instead of
a misleading error.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

neode-ui/src/components/WalletSettingsModal.vue

@@ -120,6 +120,7 @@
       </div>
 
       <div v-if="fedError" class="mb-3 alert-error">{{ fedError }}</div>
+      <div v-if="fedJoinedOk" class="mb-3 text-xs text-green-400">Federation joined.</div>
 
       <div class="flex gap-3 mt-4">
         <button @click="close" class="flex-1 glass-button px-4 py-2 rounded-lg text-sm">{{ t('common.close') }}</button>
@@ -178,6 +179,7 @@ const federations = ref<Federation[]>([])
 const inviteCode = ref('')
 const joiningFed = ref(false)
 const fedError = ref('')
+const fedJoinedOk = ref(false)
 
 watch(
   () => props.show,
@@ -259,18 +261,36 @@ async function loadFederations() {
 
 async function joinFederation() {
   if (!fedimintBackendReady || !inviteCode.value.trim()) return
+  const before = federations.value.length
   joiningFed.value = true
   fedError.value = ''
+  fedJoinedOk.value = false
   try {
     await rpcClient.call<{ federation_id: string }>({
       method: 'wallet.fedimint-join',
       params: { invite_code: inviteCode.value.trim() },
+      // Joining a federation is heavy (downloads the federation config + joins
+      // the consensus); it routinely takes longer than the default 15s. Give it
+      // headroom past the backend's own 60s clientd timeout.
+      timeout: 90000,
     })
     inviteCode.value = ''
     await loadFederations()
+    fedJoinedOk.value = true
     emit('changed')
   } catch (err: unknown) {
-    fedError.value = err instanceof Error ? err.message : 'Failed to join federation'
+    // A slow join often still completes server-side after the client gives up,
+    // so don't cry failure blindly — re-check the list. If a new federation
+    // appeared, the join actually worked; surface success instead of a scary
+    // (and wrong) timeout error.
+    await loadFederations()
+    if (federations.value.length > before) {
+      inviteCode.value = ''
+      fedJoinedOk.value = true
+      emit('changed')
+    } else {
+      fedError.value = err instanceof Error ? err.message : 'Failed to join federation'
+    }
   } finally {
     joiningFed.value = false
   }