联网搜索能力集成: opencode webfetch → 采集器

新增:
- scripts/opencode_search.py: 通过 npx opencode run 调用 webfetch 联网搜索
- 搜索缓存每日 02:30 自动刷新 (scheduler)
- 管理后台「搜索缓存」模块 + 立即运行按钮
- POST /api/system/refresh-search-cache/run 手动触发端点
- 8个分类搜索词从sources.yaml读取，调用AI联网搜索真实内容

机制:
  Python脚本 → npx opencode run → AI webfetch → 真实搜索结果 → 写入search_cache.json
  → 采集器读缓存 → LLM基于真实数据生成选题

不再需要API Key,不依赖任何搜索引擎,搜索结果来自AI的webfetch能力

platform/backend/app/api/system.py

@@ -3,6 +3,7 @@ from fastapi import APIRouter, HTTPException, Depends, Body
 from sqlalchemy.orm import Session
 from sqlalchemy import func
 from datetime import datetime, date
+from pathlib import Path
 from typing import Dict, Any, List, Optional
 from pathlib import Path
 import os
@@ -176,6 +177,22 @@ def trigger_metrics_sync():
     except Exception as e:
         raise HTTPException(status_code=500, detail=str(e))
 
+@router.post("/refresh-search-cache/run")
+def trigger_refresh_search_cache():
+    """手动刷新搜索缓存"""
+    try:
+        import subprocess, sys as sys_mod
+        scripts_dir = Path(__file__).parent.parent.parent.parent / "scripts"
+        result = subprocess.run(
+            [sys_mod.executable, str(scripts_dir / "opencode_search.py"), "--refresh-cache"],
+            capture_output=True, text=True, timeout=600
+        )
+        if result.returncode != 0:
+            raise Exception(result.stderr[-500:])
+        return {"message": "搜索缓存已刷新", "output": result.stdout.strip()}
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=str(e))
+
 @router.post("/trends/run")
 def trigger_trends_refresh():
     """手动刷新热点趋势数据"""
@@ -238,6 +255,7 @@ def get_modules_status():
     today_str = date.today().isoformat()
     log_based: dict = {
         "scheduled_collect": {"name": "📡 内容采集", "log": LOGS_DIR / f"collector_{today_str}.log"},
+        "scheduled_refresh_search_cache": {"name": "🔍 搜索缓存", "log": LOGS_DIR / f"opencode_search_{today_str}.log"},
         "scheduled_fetch_trends": {"name": "🔥 热点趋势", "log": LOGS_DIR / f"trends_{today_str}.log"},
         "scheduled_generate": {"name": "🤖 内容创作", "log": LOGS_DIR / f"creator_{today_str}.log"},
         "scheduled_optimize": {"name": "🔍 合规审查", "log": LOGS_DIR / f"optimizer_{today_str}.log"},