feat(admin): Implement operational monitoring MVP and login optimization

Summary:
- Add SimpleLog table for activity tracking (admin_schema)
- Implement ActivityService with fire-and-forget pattern
- Add stats API endpoints (overview/live-feed/user-overview/cleanup)
- Complete activity logging for 7 modules (SYSTEM/AIA/PKB/ASL/DC/RVW/IIT)
- Update Admin Dashboard with DAU/DAT metrics and live feed
- Fix user module permission display logic
- Fix login redirect to /ai-qa instead of homepage
- Replace top navigation LOGO with brand image
- Fix PKB workspace layout CSS conflict (rename to .pa-chat-container)

New files:
- backend/src/common/services/activity.service.ts
- backend/src/modules/admin/controllers/statsController.ts
- backend/src/modules/admin/routes/statsRoutes.ts
- frontend-v2/src/modules/admin/api/statsApi.ts
- docs/03-.../04-operational-monitoring-mvp-plan.md
- docs/03-.../04-operational-monitoring-mvp-implementation.md

Tested: All features verified locally

backend/src/modules/asl/services/screeningWorker.ts

@@ -13,6 +13,7 @@ import { llmScreeningService } from './llmScreeningService.js';
 import { jobQueue } from '../../../common/jobs/index.js';
 import { CheckpointService } from '../../../common/jobs/CheckpointService.js';
 import type { Job } from '../../../common/jobs/types.js';
+import { activityService } from '../../../common/services/activity.service.js';
 
 // 创建断点服务实例
 const checkpointService = new CheckpointService(prisma);
@@ -123,7 +124,7 @@ export function registerScreeningWorkers() {
       
       if (completedBatches >= totalBatches) {
         // 所有批次完成，标记任务为完成
-        await prisma.aslScreeningTask.update({
+        const task = await prisma.aslScreeningTask.update({
           where: { id: taskId },
           data: {
             status: 'completed',
@@ -131,8 +132,35 @@ export function registerScreeningWorkers() {
           },
         });
 
+        // 获取项目信息用于埋点
+        const project = await prisma.project.findUnique({
+          where: { id: task.projectId },
+        });
+
         logger.info('All batches completed, task marked as completed', { taskId });
         console.log(`\n🎉 任务 ${taskId} 全部完成！\n`);
+
+        // 埋点：记录文献筛选完成
+        try {
+          if (project) {
+            const user = await prisma.user.findUnique({
+              where: { id: project.userId },
+              include: { tenants: true }
+            });
+            if (user) {
+              activityService.log(
+                user.tenant_id,
+                user.tenants?.name || null,
+                user.id,
+                user.name,
+                'ASL',
+                '文献筛选',
+                'USE',
+                `项目:${project.name}, 文献:${totalBatches * 10}篇`
+              );
+            }
+          }
+        } catch (e) { /* 埋点失败不影响主业务 */ }
       }
       
     } catch (error) {