feat: complete client billing UI and staff benefits display (#524, #527)

- Client App: Built dedicated ShiftCompletionReviewPage  and InvoiceReadyPage
- Client App: Wired up invoice summary mapping and parsing logic from Data Connect
- Staff App: Added dynamic BenefitsOverviewPage tracking worker limits matching client mockup
- Staff App: Display progress ring values wired to real VendorBenefitPlan & BenefitsData balances

apps/mobile/packages/domain/lib/src/entities/benefits/benefit.dart

@@ -0,0 +1,26 @@
+import 'package:equatable/equatable.dart';
+
+/// Represents a staff member's benefit balance.
+class Benefit extends Equatable {
+  /// The title of the benefit (e.g., Sick Leave, Holiday, Vacation).
+  final String title;
+
+  /// The total entitlement in hours.
+  final double entitlementHours;
+
+  /// The hours used so far.
+  final double usedHours;
+
+  /// The hours remaining.
+  double get remainingHours => entitlementHours - usedHours;
+
+  /// Creates a [Benefit].
+  const Benefit({
+    required this.title,
+    required this.entitlementHours,
+    required this.usedHours,
+  });
+
+  @override
+  List<Object?> get props => [title, entitlementHours, usedHours];
+}