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/core/scheduler.py

@@ -62,6 +62,14 @@ class TaskScheduler:
             max_instances=1,
             coalesce=True
         )
+        self.scheduler.add_job(
+            self._run_refresh_search_cache,
+            CronTrigger(hour=2, minute=30),
+            id='scheduled_refresh_search_cache',
+            replace_existing=True,
+            max_instances=1,
+            coalesce=True
+        )
         self.scheduler.add_job(
             self._run_metrics_sync,
             CronTrigger(hour=6, minute=0),
@@ -72,7 +80,7 @@ class TaskScheduler:
         )
         self.scheduler.start()
         self._started = True
-        logger.info("Scheduler started: 01:30 collect, 03:00 trends, 03:30 generate, 04:30 review, 05:00 optimize_sources, 06:00 metrics_sync")
+        logger.info("Scheduler started: 01:30 collect, 02:30 refresh_search, 03:00 trends, 03:30 generate, 04:30 review, 05:00 optimize_sources, 06:00 metrics_sync")
     def shutdown(self):
         if self.scheduler.running:
             self.scheduler.shutdown()
@@ -97,6 +105,30 @@ class TaskScheduler:
         except Exception as e:
             logger.exception("[Scheduled] Trends refresh error: %s", e)
 
+    def _run_refresh_search_cache(self):
+        """定时刷新搜索缓存（通过 opencode webfetch）"""
+        try:
+            logger.info("[Scheduled] Refreshing search cache via opencode...")
+            import subprocess
+            result = subprocess.run(
+                [sys.executable, str(Path(__file__).parent.parent.parent.parent / "scripts" / "opencode_search.py"), "--refresh-cache"],
+                capture_output=True, text=True, timeout=600
+            )
+            for line in result.stdout.strip().split("\n"):
+                if line.strip():
+                    logger.info("[SearchCache] %s", line.strip())
+            for line in result.stderr.strip().split("\n"):
+                if line.strip():
+                    logger.warning("[SearchCache] %s", line.strip())
+            if result.returncode == 0:
+                logger.info("[Scheduled] Search cache refreshed")
+            else:
+                logger.warning("[Scheduled] Search cache refresh may have partial failures")
+        except subprocess.TimeoutExpired:
+            logger.warning("[Scheduled] Search cache refresh timed out")
+        except Exception as e:
+            logger.exception("[Scheduled] Search cache refresh error: %s", e)
+
     def _run_generate(self):
         try:
             logger.info("[Scheduled] Starting content generation...")