refactor: 全面重构核心架构，消除反复修改的根因

- 删除 ValidationQueue 双轨持久化队列，替换为纯内存 AsyncWorkerPool
- 引入统一后台任务框架 JobExecutor（Job/CrawlJob/ValidateAllJob）
- 新增 PluginRunner 统一插件执行（超时、重试、健康检查、统计）
- 重构 SchedulerService 职责收敛为仅定时触发 ValidateAllJob
- 使用 AsyncExitStack 重构 lifespan，安全管理长生命周期资源
- 路由层瘦身 50%+，业务异常上抛由全局中间件统一处理
- 实现设置全热更新（WorkerPool 并发、Validator 超时即时生效）
- 前端 Store 强制写后重新拉取，消除乐观更新数据不同步
- 删除 queue.py / task_repo.py / task_service.py
- 新增 execution 单元测试，全部 85 个测试通过

app/api/routes/settings.py

@@ -3,7 +3,7 @@ from fastapi import APIRouter, Request
 from app.core.db import get_db
 from app.repositories.settings_repo import SettingsRepository
 from app.models.schemas import SettingsSchema
-from app.api.common import success_response, error_response
+from app.api.common import success_response
 from app.core.log import logger
 
 router = APIRouter(prefix="/api/settings", tags=["settings"])
@@ -22,14 +22,32 @@ async def save_settings(request: SettingsSchema, http_request: Request):
     async with get_db() as db:
         success = await settings_repo.save(db, request.model_dump())
     if not success:
-        return error_response("保存设置失败", 500)
+        raise RuntimeError("保存设置失败")
 
     # 热更新运行中调度器的间隔时间
-    scheduler = getattr(http_request.app.state, "scheduler_service", None)
-    if scheduler and scheduler.running:
+    scheduler = getattr(http_request.app.state, "scheduler", None)
+    worker_pool = getattr(http_request.app.state, "worker_pool", None)
+    validator = getattr(http_request.app.state, "validator", None)
+
+    if scheduler:
         new_interval = request.validate_interval_minutes
         if scheduler.interval_minutes != new_interval:
             scheduler.interval_minutes = new_interval
             logger.info(f"Scheduler interval updated to {new_interval} minutes")
 
+    # 热更新 Worker 池大小
+    if worker_pool and worker_pool.worker_count != request.default_concurrency:
+        await worker_pool.resize(request.default_concurrency)
+        logger.info(f"Worker pool resized to {request.default_concurrency}")
+
+    # 热更新验证器超时和并发（下次验证时生效）
+    if validator:
+        validator._init_timeout = request.validation_timeout
+        validator._init_connect_timeout = request.validation_timeout
+        validator._init_max_concurrency = request.default_concurrency
+        # 重新创建 semaphore 和 session
+        validator._semaphore = None
+        await validator.close()
+        logger.info(f"Validator config updated: timeout={request.validation_timeout}, concurrency={request.default_concurrency}")
+
     return success_response("保存设置成功", request.model_dump())