Phase 4: Template system with auto-select and pre-fill

Backend:
- Add templates.json with 5 template definitions (news, policy, business, fiction, social)
- Add template API (/api/template/list, /api/template/auto-select, /api/template/:id/filter-rules)
- Register template blueprint in Flask app

Frontend:
- Add template API client (frontend/src/api/template.js)
- Add template selector UI in Home.vue (chip buttons + auto-select button)
- Add template state management and auto-select logic

Locale:
- Add template keys for th/en/zh

Entity filter rules in templates.json for context-aware filtering in Step 1.

locales/zh.json

@@ -677,5 +677,16 @@
     "llmSelectAgentFailed": "LLM选择Agent失败，使用默认选择: {error}",
     "generateInterviewQuestionsFailed": "生成采访问题失败: {error}",
     "generateInterviewSummaryFailed": "生成采访摘要失败: {error}"
+  },
+  "templates": {
+    "title": "选择模拟模板",
+    "autoSelect": "从数据自动推荐",
+    "custom": "自行编写",
+    "news_event": "新闻与事件",
+    "policy_regulation": "政策与法规",
+    "business_ad": "商业与广告",
+    "fiction_story": "小说与故事",
+    "social_culture": "社会与文化",
+    "fillPrompt": "运行前编辑指令"
   }
 }