feat: Update voice design tab labels for consistency across languages

qwen3-tts-frontend/src/locales/en-US/nav.json

@@ -7,6 +7,6 @@
   "toggleTheme": "Toggle Theme",
   "changeLanguage": "Change Language",
   "customVoiceTab": "Custom",
-  "voiceDesignTab": "Design",
+  "voiceDesignTab": "Create Voice",
   "voiceCloneTab": "Clone"
 }

qwen3-tts-frontend/src/locales/ja-JP/nav.json

@@ -7,6 +7,6 @@
   "toggleTheme": "テーマ切替",
   "changeLanguage": "言語変更",
   "customVoiceTab": "カスタム",
-  "voiceDesignTab": "デザイン",
+  "voiceDesignTab": "音色作成",
   "voiceCloneTab": "クローン"
 }

qwen3-tts-frontend/src/locales/ko-KR/nav.json

@@ -7,6 +7,6 @@
   "toggleTheme": "테마 전환",
   "changeLanguage": "언어 변경",
   "customVoiceTab": "커스텀",
-  "voiceDesignTab": "디자인",
+  "voiceDesignTab": "음색 생성",
   "voiceCloneTab": "복제"
 }

qwen3-tts-frontend/src/locales/zh-CN/nav.json

@@ -7,6 +7,6 @@
   "toggleTheme": "切换主题",
   "changeLanguage": "切换语言",
   "customVoiceTab": "自定义",
-  "voiceDesignTab": "设计",
+  "voiceDesignTab": "创造音色",
   "voiceCloneTab": "克隆"
 }

qwen3-tts-frontend/src/locales/zh-TW/nav.json

@@ -7,6 +7,6 @@
   "toggleTheme": "切換主題",
   "changeLanguage": "切換語言",
   "customVoiceTab": "自訂",
-  "voiceDesignTab": "設計",
+  "voiceDesignTab": "創造音色",
   "voiceCloneTab": "複製"
 }