style: 優化重組區域置中效果與註解規範

## 重組區域視覺改進
- 修正「答案區」完全置中對齊（上下左右都置中）
- 使用 absolute inset-0 確保完美居中效果
- 添加 relative 定位支援絕對定位子元素

## 代碼註解規範
- 為所有測驗說明文字添加統一註解格式
- 使用 "Instructions Test Action" 標準註解
- 提升代碼可讀性和維護性

## 布局微調
- 優化重組區域的空白狀態顯示
- 確保視覺元素的精確對齊

🤖 Generated with [Claude Code](https://claude.ai/code)

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

frontend/app/learn/page.tsx

@@ -447,7 +447,9 @@ export default function LearnPage() {
                         {currentCard.difficulty}
                       </span>
                     </div>
-                    <p className="text-lg text-gray-700 mb-2 text-left">
+
+                    {/* Instructions Test Action */}
+                    <p className="text-lg text-gray-700 mb-6 text-left">
                       點擊卡片翻面，根據你對單字的熟悉程度進行自我評估：
                     </p>
 
@@ -557,9 +559,12 @@ export default function LearnPage() {
                   {currentCard.difficulty}
                 </span>
               </div>
-              <p className="text-lg text-gray-700 mb-2 text-left">
+
+              {/* Instructions Test Action */}
+              <p className="text-lg text-gray-700 mb-6 text-left">
                 請選擇符合上述定義的英文詞彙：
               </p>
+
               <div className="text-center mb-8">
                 <div className="bg-gray-50 rounded-lg p-4 mb-6">
                   <h3 className="font-semibold text-gray-900 mb-2 text-left">定義</h3>
@@ -681,9 +686,12 @@ export default function LearnPage() {
                   </div>
                 </div>
               )}
-            <p className="text-lg text-gray-700 mb-2 text-left">
+
+              {/* Instructions Test Action */}
+            <p className="text-lg text-gray-700 mb-6 text-left">
                 請點擊例句中的空白處輸入正確的單字：
               </p>
+              
               {/* Example Sentence with Blanks */}
               <div className="mb-6">
                 <div className="bg-gray-50 rounded-lg p-6">
@@ -833,7 +841,9 @@ export default function LearnPage() {
                   {currentCard.difficulty}
                 </span>
               </div>
-              <p className="text-lg text-gray-700 mb-2 text-left">
+
+              {/* Instructions Test Action */}
+              <p className="text-lg text-gray-700 mb-6 text-left">
                 請聽發音並選擇正確的英文單字：
               </p>
 
@@ -1010,7 +1020,9 @@ export default function LearnPage() {
                   {currentCard.difficulty}
                 </span>
               </div>
-              <p className="text-lg text-gray-700 mb-2 text-left">
+
+              {/* Instructions Test Action */}
+              <p className="text-lg text-gray-700 mb-6 text-left">
                 請聽例句並選擇正確的選項：
               </p>
 
@@ -1090,17 +1102,16 @@ export default function LearnPage() {
                   </div>
                 </div>
               )}
-             <p className="text-lg text-gray-700 mb-2 text-left">
-                點擊下方單字，依序重組成正確的句子：
-              </p>
-              
+
+
+
               {/* Arranged Sentence Area */}
               <div className="mb-6">
                 <h3 className="text-lg font-semibold text-gray-900 mb-3 text-left">重組區域：</h3>
-                <div className="min-h-[120px] bg-gray-50 rounded-lg p-4 border-2 border-dashed border-gray-300">
+                <div className="relative min-h-[120px] bg-gray-50 rounded-lg p-4 border-2 border-dashed border-gray-300">
                   {arrangedWords.length === 0 ? (
-                    <div className="flex items-center justify-center h-full text-gray-400 text-lg">
-                      點擊下方單字來重組句子
+                    <div className="absolute inset-0 flex items-center justify-center text-gray-400 text-lg">
+                      答案區
                     </div>
                   ) : (
                     <div className="flex flex-wrap gap-2">
@@ -1119,6 +1130,11 @@ export default function LearnPage() {
                 </div>
               </div>
 
+              {/* Instructions Test Action */}
+              <p className="text-lg text-gray-700 mb-6 text-left">
+                點擊下方單字，依序重組成正確的句子：
+              </p>
+              
               {/* Shuffled Words */}
               <div className="mb-6">
                 <h3 className="text-lg font-semibold text-gray-900 mb-3 text-left">可用單字：</h3>

frontend/components/VoiceRecorder.tsx

@@ -257,14 +257,6 @@ export default function VoiceRecorder({
         </div>
       )}
 
-      {/* Instruction Text */}
-      {instructionText && (
-        <div className="mb-6">
-          <p className="text-lg text-gray-700 text-left">
-            {instructionText}
-          </p>
-        </div>
-      )}
 
       {/* 目標文字顯示 */}
       <div className="mb-6">
@@ -284,6 +276,15 @@ export default function VoiceRecorder({
         </div>
       </div>
 
+      {/* Instruction Text */}
+      {instructionText && (
+        <div className="mb-6">
+          <p className="text-lg text-gray-700 text-left">
+            {instructionText}
+          </p>
+        </div>
+      )}
+      
       {/* 錄音控制區 */}
       <div className="p-6 border-2 border-dashed border-gray-300 rounded-xl">
         <div className="flex flex-col items-center gap-4">