feat(home): add AI story expand button and modal

messages/zh/home.json

@@ -11,5 +11,15 @@
     "minutesAgo": "{n}分钟前",
     "hoursAgo": "{n}小时前",
     "daysAgo": "{n}天前"
+  },
+  "aiWrite": {
+    "trigger": "AI 帮我写",
+    "modalTitle": "AI 创作助手",
+    "modalSubtitle": "输入你的创意，让 AI 帮你生成完整故事",
+    "inputLabel": "输入你的创意内容",
+    "placeholder": "输入关键词、故事大纲或简短创意...\n\n例如：\n• 古代宫廷 复仇 悬疑 女主角\n• 第一幕：女主回到京城，暗访旧宅；第二幕：宫廷宴会偶遇仇人之子",
+    "hint": "💡 可以输入关键词、故事大纲、创意描述，AI 会根据你的输入扩展生成完整的故事内容",
+    "startAiWrite": "开始 AI 创作",
+    "cancel": "取消"
   }
 }

messages/zh/progress.json

@@ -65,6 +65,7 @@
     "screenplayConvert": "剧本转换",
     "voiceAnalyze": "台词分析",
     "analyzeGlobal": "全局分析",
+    "aiStoryExpand": "AI 故事扩写",
     "aiModifyAppearance": "角色描述修改",
     "aiModifyLocation": "场景描述修改",
     "aiModifyShotPrompt": "镜头提示词修改",
@@ -104,6 +105,8 @@
     "scriptToStoryboardStep": "执行分镜生成步骤",
     "scriptToStoryboardPersist": "保存分镜结果",
     "scriptToStoryboardPersistDone": "分镜与台词结果已保存",
+    "aiStoryExpandPrepare": "准备故事扩写参数",
+    "aiStoryExpandDone": "故事扩写已完成",
     "insertPanelGenerateText": "生成插入镜头文本",
     "insertPanelPersist": "保存插入镜头",
     "pollingExternal": "等待外部服务返回",