重构: 迁移后端代码到 app 目录，前端移动到 WebUI，添加完整测试套件

主要变更:
- 后端代码从根目录迁移到 app/ 目录
- 前端代码从 frontend/ 重命名为 WebUI/
- 更新所有导入路径以适配新结构
- 提取公共 API 响应函数到 app/api/common.py
- 精简验证器服务代码
- 更新启动脚本和文档

测试:
- 新增完整测试套件 (tests/)
- 单元测试: 模型、仓库层
- 集成测试: 覆盖所有 22+ API 端点
- E2E 测试: 4个完整工作流场景
- 添加 pytest 配置和测试运行脚本

app/api/routes/scheduler.py

@@ -0,0 +1,64 @@
+"""调度器相关路由"""
+from fastapi import APIRouter, Depends
+from app.services.scheduler_service import SchedulerService
+from app.repositories.settings_repo import SettingsRepository
+from app.core.db import get_db
+from app.api.deps import get_scheduler_service
+from app.api.common import success_response, error_response
+from app.core.log import logger
+
+router = APIRouter(prefix="/api/scheduler", tags=["scheduler"])
+settings_repo = SettingsRepository()
+
+
+async def _save_auto_validate_setting(enabled: bool):
+    """保存自动验证设置"""
+    async with get_db() as db:
+        settings = await settings_repo.get_all(db)
+        settings["auto_validate"] = enabled
+        from app.models.schemas import SettingsSchema
+        await settings_repo.save(db, SettingsSchema(**settings).model_dump())
+
+
+@router.post("/start")
+async def start_scheduler(scheduler: SchedulerService = Depends(get_scheduler_service)):
+    try:
+        if scheduler.running:
+            return success_response("验证调度器已在运行", {"running": True})
+        await scheduler.start()
+        await _save_auto_validate_setting(True)
+        return success_response("验证调度器已启动", {"running": True})
+    except Exception as e:
+        logger.error(f"Start scheduler failed: {e}")
+        return error_response(f"启动调度器失败: {str(e)}", 500)
+
+
+@router.post("/stop")
+async def stop_scheduler(scheduler: SchedulerService = Depends(get_scheduler_service)):
+    try:
+        if not scheduler.running:
+            return success_response("验证调度器未运行", {"running": False})
+        await scheduler.stop()
+        await _save_auto_validate_setting(False)
+        return success_response("验证调度器已停止", {"running": False})
+    except Exception as e:
+        logger.error(f"Stop scheduler failed: {e}")
+        return error_response(f"停止调度器失败: {str(e)}", 500)
+
+
+@router.post("/validate-now")
+async def validate_now(scheduler: SchedulerService = Depends(get_scheduler_service)):
+    try:
+        scheduler.validate_all_now()
+        return success_response("已开始全量验证", {"started": True})
+    except Exception as e:
+        logger.error(f"Validate now failed: {e}")
+        return error_response(f"启动验证失败: {str(e)}", 500)
+
+
+@router.get("/status")
+async def scheduler_status(scheduler: SchedulerService = Depends(get_scheduler_service)):
+    return success_response(
+        "获取状态成功",
+        {"running": scheduler.running, "interval_minutes": scheduler.interval_minutes},
+    )