Enhance AppSettings and RentController to manage not-occupied months, add lifetime summary to SettingsScreen, and update tests for compatibility

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

lib/screens/settings_screen.dart

@@ -1,5 +1,6 @@
 import 'package:file_picker/file_picker.dart';
 import 'package:flutter/material.dart';
+import 'package:intl/intl.dart';
 import 'package:provider/provider.dart';
 import 'package:rental_income_tracker/state/rent_controller.dart';
 
@@ -56,11 +57,45 @@ class _SettingsScreenState extends State<SettingsScreen> {
   Widget build(BuildContext context) {
     return Consumer<RentController>(
       builder: (context, controller, _) {
+        final summary = controller.buildLifetimeSummary();
+        final usdCurrency = NumberFormat.currency(
+          symbol: r'$',
+          decimalDigits: 2,
+        );
+        final sekCurrency = NumberFormat.currency(
+          symbol: 'SEK ',
+          decimalDigits: 2,
+        );
+
         return Scaffold(
           appBar: AppBar(title: const Text('Settings')),
           body: ListView(
             padding: const EdgeInsets.all(16),
             children: <Widget>[
+              Card(
+                child: Padding(
+                  padding: const EdgeInsets.all(16),
+                  child: Column(
+                    crossAxisAlignment: CrossAxisAlignment.start,
+                    children: <Widget>[
+                      Text(
+                        'All-time totals (since May 2024)',
+                        style: Theme.of(context).textTheme.titleMedium,
+                      ),
+                      const SizedBox(height: 8),
+                      Text(
+                        '${usdCurrency.format(summary.totalUsd)} | ${sekCurrency.format(summary.totalSek)}',
+                        style: Theme.of(context).textTheme.titleLarge,
+                      ),
+                      const SizedBox(height: 4),
+                      Text(
+                        'Occupancy: ${summary.occupancyPercent.toStringAsFixed(1)}% (${summary.occupiedMonths}/${summary.totalTrackedMonths} months)',
+                      ),
+                    ],
+                  ),
+                ),
+              ),
+              const SizedBox(height: 12),
               TextField(
                 controller: _rentController,
                 keyboardType: const TextInputType.numberWithOptions(