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/en.json

@@ -677,5 +677,16 @@
     "llmSelectAgentFailed": "LLM agent selection failed, using default selection: {error}",
     "generateInterviewQuestionsFailed": "Failed to generate interview questions: {error}",
     "generateInterviewSummaryFailed": "Failed to generate interview summary: {error}"
+  },
+  "templates": {
+    "title": "Select simulation template",
+    "autoSelect": "Auto-select from data",
+    "custom": "Write your own",
+    "news_event": "News & Events",
+    "policy_regulation": "Policy & Regulations",
+    "business_ad": "Business & Advertising",
+    "fiction_story": "Fiction & Stories",
+    "social_culture": "Social & Culture",
+    "fillPrompt": "Edit prompt before running"
   }
 }