feat: update analytics services for improved task handling

- Removed unused `parseDate` import from `analytics.ts`.
- Refactored `ManagerSummaryService` to handle standalone todos with a new priority rule, ensuring todos without tasks default to low priority.
- Updated logic in `MetricsService` to calculate total tasks by including in-progress tasks, enhancing completion rate accuracy.
- Adjusted comments for clarity on new functionality and priority determination.

src/services/analytics/analytics.ts

@@ -1,6 +1,6 @@
 import { Task, TaskStatus, TaskPriority, TaskSource } from '@/lib/types';
 import { prisma } from '@/services/core/database';
-import { getToday, parseDate, subtractDays } from '@/lib/date-utils';
+import { getToday, subtractDays } from '@/lib/date-utils';
 
 export interface ProductivityMetrics {
   completionTrend: Array<{