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/utils/staff_presence.dart

@@ -0,0 +1,63 @@
+import 'package:tasq/models/leave_of_absence.model.dart';
+import 'package:tasq/models/pass_slip.model.dart';
+import 'programmer_daily_time.dart';
+
+/// Index approved leaves covering the given moment by user ID.
+///
+/// Filters to leaves where:
+/// - status == 'approved'
+/// - startTime <= now < endTime
+///
+/// Returns a map from userId to the leave record.
+Map<String, LeaveOfAbsence> activeLeaveByUser(
+  List<LeaveOfAbsence> leaves,
+  DateTime now,
+) {
+  final result = <String, LeaveOfAbsence>{};
+  for (final leave in leaves) {
+    if (leave.status == 'approved' &&
+        !leave.startTime.isAfter(now) &&
+        leave.endTime.isAfter(now)) {
+      result[leave.userId] = leave;
+    }
+  }
+  return result;
+}
+
+/// Index active pass slips by user ID.
+///
+/// Filters to slips where slip.isActive is true.
+///
+/// Returns a map from userId to the pass slip record.
+Map<String, PassSlip> activePassSlipByUser(List<PassSlip> slips) {
+  final result = <String, PassSlip>{};
+  for (final slip in slips) {
+    if (slip.isActive) {
+      result[slip.userId] = slip;
+    }
+  }
+  return result;
+}
+
+/// Get the set of Manila calendar days covered by approved leaves for a user.
+///
+/// Iterates through all approved leaves for the given user and collects the
+/// set of Manila day keys (as DateTime.utc(year, month, day)) from each
+/// leave's start date through end date, inclusive.
+Set<DateTime> approvedLeaveDays(
+  List<LeaveOfAbsence> leaves,
+  String userId,
+) {
+  final result = <DateTime>{};
+  for (final leave in leaves) {
+    if (leave.userId == userId && leave.status == 'approved') {
+      var current = manilaDay(leave.startTime);
+      final endDay = manilaDay(leave.endTime);
+      while (!current.isAfter(endDay)) {
+        result.add(current);
+        current = current.add(Duration(days: 1));
+      }
+    }
+  }
+  return result;
+}