refactor: extract staff presence helpers

- Extract activeLeaveByUser, activePassSlipByUser, and approvedLeaveDays to staff_presence.dart utility module
- Replace inline indexing loops in dashboard_screen.dart with helper function calls
- Behavior unchanged, tests added covering all functions

Co-Authored-By: claude-flow <ruv@ruv.net>

lib/screens/dashboard/dashboard_screen.dart

@@ -44,6 +44,7 @@ import '../../widgets/app_metric_card.dart';
 import '../../widgets/app_page_header.dart';
 import '../../widgets/app_section_header.dart';
 import '../../utils/app_time.dart';
+import '../../utils/staff_presence.dart' as staff_presence;
 
 class DashboardMetrics {
   DashboardMetrics({
@@ -369,22 +370,10 @@ final dashboardMetricsProvider = Provider<AsyncValue<DashboardMetrics>>((ref) {
   }
 
   // Index today's leaves by user.
-  final todayLeaveByUser = <String, LeaveOfAbsence>{};
-  for (final l in allLeaves) {
-    if (l.status == 'approved' &&
-        !l.startTime.isAfter(now) &&
-        l.endTime.isAfter(now)) {
-      todayLeaveByUser[l.userId] = l;
-    }
-  }
+  final todayLeaveByUser = staff_presence.activeLeaveByUser(allLeaves, now);
 
   // Index active pass slips by user.
-  final activePassSlipByUser = <String, PassSlip>{};
-  for (final slip in allPassSlips) {
-    if (slip.isActive) {
-      activePassSlipByUser[slip.userId] = slip;
-    }
-  }
+  final activePassSlipByUser = staff_presence.activePassSlipByUser(allPassSlips);
 
   final noon = DateTime(now.year, now.month, now.day, 12, 0);
   final onePM = DateTime(now.year, now.month, now.day, 13, 0);