feat(ai): redesign AI assistant as right-side chat panel

- Chat-style conversation UI with message bubbles
- Multi-turn dialog with context history
- SQL code blocks with "Apply" and "Copy" buttons
- Toggle via Sparkles button in toolbar
- Settings dialog preserved

src/i18n/locales/zh-CN.ts

@@ -138,6 +138,10 @@ export default {
     copied: "已复制",
     replace: "替换编辑器",
     append: "追加到编辑器",
+    apply: "应用到编辑器",
+    clear: "清空对话",
+    welcome: "输入问题，AI 帮你生成 SQL",
+    thinking: "思考中...",
     truncated: "上下文已截断",
     contextSummary: "{database} · {tables} 张表",
     settingsHint: "配置会保存在本机应用数据目录中。请求由 Tauri 后端发出，避免在前端直接暴露给模型服务。",