Can backfill the previous year, although some API rate limiting but it works

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

lib/state/rent_controller.dart

@@ -241,8 +241,20 @@ class RentController extends ChangeNotifier {
       }
 
       final year = DateTime.now().year - 1;
+
+      // Attempt a single timeseries call covering the whole year.
+      final batchRates = await _exchangeService.tryFetchYearRates(year);
+      if (kDebugMode) {
+        debugPrint(
+          batchRates != null
+              ? '[RentController] backfill using batch timeseries (${batchRates.length} dates)'
+              : '[RentController] backfill falling back to individual daily requests',
+        );
+      }
+
       var savedMonths = 0;
       var pausedByRateLimit = false;
+      var isFirstIndividualFetch = true;
 
       for (var month = 1; month <= 12; month++) {
         final key = TimeService.monthKey(year, month);
@@ -256,10 +268,29 @@ class RentController extends ChangeNotifier {
         try {
           final usd = _settings.rentUsd;
           final estDate = DateTime(year, month, 1);
-          final conversion = await _exchangeService.convertUsdToSek(
-            estDate: estDate,
-            amount: usd,
-          );
+
+          final ForexConversionResult conversion;
+          if (batchRates != null) {
+            final dateStr = DateFormat('yyyy-MM-dd').format(estDate);
+            final quote = batchRates[dateStr];
+            if (quote == null) {
+              throw StateError('Batch rates missing entry for $dateStr.');
+            }
+            conversion = ForexConversionResult(
+              quote: quote,
+              result: quote * usd,
+            );
+          } else {
+            // Pace individual requests to avoid triggering the rate limit.
+            if (!isFirstIndividualFetch) {
+              await Future.delayed(const Duration(milliseconds: 700));
+            }
+            isFirstIndividualFetch = false;
+            conversion = await _exchangeService.convertUsdToSek(
+              estDate: estDate,
+              amount: usd,
+            );
+          }
 
           if (kDebugMode) {
             debugPrint(