Fix medium priority issues from code review

- Add DEPLOY_TIMING constants for deployment simulation
- Add null checks in switchTab function for consistency
- Add role="radiogroup" and fieldset/legend to wizard steps
- Add role="log" and aria-live="polite" to chat container
- Add bottom border to active pricing region button for better visual distinction

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app.js

@@ -58,6 +58,14 @@ const PAYMENT_METHODS = [
   { id: 'yearly', name: '연간 결제', desc: '2개월 무료 (17% 할인)', discount: 17 }
 ];
 
+// 배포 시뮬레이션 타이밍 상수
+const DEPLOY_TIMING = {
+  IMAGE_READY: 1500,
+  CONTAINER_CREATED: 3000,
+  NETWORK_CONFIGURED: 4500,
+  COMPLETE: 6000
+};
+
 /**
  * 가격 포맷팅 (한국 원화)
  */
@@ -197,26 +205,26 @@ function anvilApp() {
         this.logs.push('✅ 이미지 준비 완료');
         this.logs.push('🔧 컨테이너 인스턴스 생성 중...');
         this.deployStep = 2;
-      }, 1500);
+      }, DEPLOY_TIMING.IMAGE_READY);
 
       setTimeout(() => {
         this.logs.push('✅ 컨테이너 생성 완료');
         this.logs.push('🌐 네트워크 및 방화벽 구성 중...');
         this.deployStep = 3;
-      }, 3000);
+      }, DEPLOY_TIMING.CONTAINER_CREATED);
 
       setTimeout(() => {
         const randomIP = Math.floor(Math.random() * 254 + 1);
         this.logs.push(`✅ IP 할당 완료: 45.12.89.${randomIP}`);
         this.logs.push('⚙️ 시스템 서비스 시작 중...');
         this.deployStep = 4;
-      }, 4500);
+      }, DEPLOY_TIMING.NETWORK_CONFIGURED);
 
       setTimeout(() => {
         this.launching = false;
         this.deployStep = 5;
         this.logs.push('🎉 서버가 활성화되었습니다!');
-      }, 6000);
+      }, DEPLOY_TIMING.COMPLETE);
     },
 
     // 런처 열기
@@ -275,6 +283,9 @@ function switchTab(tab) {
   const panelN8n = document.getElementById('panel-n8n');
   const panelTf = document.getElementById('panel-tf');
 
+  // Null checks for DOM elements
+  if (!btnN8n || !btnTf || !panelN8n || !panelTf) return;
+
   if (tab === 'n8n') {
     // Update ARIA states for n8n tab
     btnN8n.setAttribute('aria-selected', 'true');

index.html

@@ -551,11 +551,11 @@
         <!-- Tab Buttons -->
         <div class="flex justify-center mb-8">
           <div class="glass-panel p-1.5 rounded-2xl inline-flex gap-1">
-            <button @click="region = 'global'" :class="region === 'global' ? 'bg-gradient-to-r from-brand-600 to-brand-500 text-white shadow-lg shadow-brand-500/30' : 'text-slate-400 hover:text-white hover:bg-white/5'" class="px-6 py-3 rounded-xl text-sm font-bold transition-all flex items-center gap-2">
+            <button @click="region = 'global'" :class="region === 'global' ? 'bg-gradient-to-r from-brand-600 to-brand-500 text-white shadow-lg shadow-brand-500/30 border-b-2 border-b-white/60' : 'text-slate-400 hover:text-white hover:bg-white/5'" class="px-6 py-3 rounded-xl text-sm font-bold transition-all flex items-center gap-2">
               <span>🌏 Global</span>
               <span class="text-[10px] font-normal opacity-80">(Tokyo/SG/HK)</span>
             </button>
-            <button @click="region = 'seoul'" :class="region === 'seoul' ? 'bg-gradient-to-r from-brand-600 to-brand-500 text-white shadow-lg shadow-brand-500/30' : 'text-slate-400 hover:text-white hover:bg-white/5'" class="px-6 py-3 rounded-xl text-sm font-bold transition-all flex items-center gap-2">
+            <button @click="region = 'seoul'" :class="region === 'seoul' ? 'bg-gradient-to-r from-brand-600 to-brand-500 text-white shadow-lg shadow-brand-500/30 border-b-2 border-b-white/60' : 'text-slate-400 hover:text-white hover:bg-white/5'" class="px-6 py-3 rounded-xl text-sm font-bold transition-all flex items-center gap-2">
               <span>🇰🇷 Seoul</span>
               <span class="text-[10px] font-normal opacity-80">(Premium)</span>
             </button>
@@ -774,7 +774,7 @@
         </div>
 
         <!-- Chat Container -->
-        <div id="chat-container" class="flex-1 overflow-y-auto px-3 sm:px-6 py-3 sm:py-4 space-y-2 sm:space-y-4" x-show="wizardStep < 5">
+        <div id="chat-container" role="log" aria-live="polite" class="flex-1 overflow-y-auto px-3 sm:px-6 py-3 sm:py-4 space-y-2 sm:space-y-4" x-show="wizardStep < 5">
           <!-- Messages -->
           <template x-for="(msg, idx) in messages" :key="idx">
             <div :class="msg.type === 'bot' ? 'flex justify-start' : 'flex justify-end'"
@@ -793,7 +793,7 @@
           <!-- Current Step Options -->
           <div class="pt-2">
             <!-- Step 0: Region Selection -->
-            <fieldset x-show="wizardStep === 0" class="space-y-3">
+            <fieldset x-show="wizardStep === 0" role="radiogroup" aria-label="리전 선택" class="space-y-3">
               <legend class="sr-only">리전 선택 (지역 선택)</legend>
               <template x-for="r in regions" :key="r.id">
                 <button @click="selectRegion(r)"
@@ -817,7 +817,8 @@
             </fieldset>
 
             <!-- Step 1: Plan Selection -->
-            <div x-show="wizardStep === 1" class="space-y-3">
+            <fieldset x-show="wizardStep === 1" class="space-y-3">
+              <legend class="sr-only">플랜 선택 (서버 사양 선택)</legend>
               <template x-for="p in plans" :key="p">
                 <button @click="selectPlan(p)"
                         class="w-full flex items-center justify-between px-5 py-4 bg-slate-800/80 hover:bg-slate-700 border border-slate-700/50 hover:border-brand-500/50 rounded-xl transition-all">
@@ -835,10 +836,11 @@
                   </div>
                 </button>
               </template>
-            </div>
+            </fieldset>
 
             <!-- Step 2: OS Selection -->
-            <div x-show="wizardStep === 2" class="space-y-3">
+            <fieldset x-show="wizardStep === 2" class="space-y-3">
+              <legend class="sr-only">운영체제 선택</legend>
               <template x-for="os in osList" :key="os.id">
                 <button @click="selectOS(os)"
                         class="w-full flex items-center gap-4 px-5 py-4 bg-slate-800/80 hover:bg-slate-700 border border-slate-700/50 hover:border-purple-500/50 rounded-xl transition-all">
@@ -846,10 +848,11 @@
                   <span class="font-semibold text-white text-base" x-text="os.name"></span>
                 </button>
               </template>
-            </div>
+            </fieldset>
 
             <!-- Step 3: Payment Selection -->
-            <div x-show="wizardStep === 3" class="space-y-3">
+            <fieldset x-show="wizardStep === 3" class="space-y-3">
+              <legend class="sr-only">결제 방식 선택</legend>
               <template x-for="pay in paymentMethods" :key="pay.id">
                 <button @click="selectPayment(pay)"
                         class="w-full flex items-center justify-between px-5 py-4 bg-slate-800/80 hover:bg-slate-700 border border-slate-700/50 hover:border-green-500/50 rounded-xl transition-all">
@@ -862,7 +865,7 @@
                   </div>
                 </button>
               </template>
-            </div>
+            </fieldset>
 
             <!-- Step 4: Confirmation -->
             <div x-show="wizardStep === 4" class="space-y-4">