Add voice selection control

Expose a voice selector next to the save button and pass the choice to TTS so pyttsx3 can prefer a female voice.

client/templates/index.html

@@ -11,7 +11,13 @@
       <section class="panel left">
         <div class="panel-header">입력 텍스트</div>
         <textarea id="text-input" rows="16" placeholder="텍스트를 입력하세요"></textarea>
-        <button id="save-btn" class="primary">mp3 저장</button>
+        <div class="save-row">
+          <button id="save-btn" class="primary">mp3 변환</button>
+          <select id="voice-select" class="voice-select" aria-label="음성 선택">
+            <option value="male">남성#1</option>
+            <option value="female">여성#1</option>
+          </select>
+        </div>
         <div id="save-progress" class="progress-wrap hidden" aria-label="저장 진행률">
           <div
             id="save-progress-bar"