Fix widget gap: forward-fill months and use reference month date for batch update

BatchUpdateView now accepts a saveDate parameter. When saving from a past-month
check-in, the call site passes referenceDate.endOfMonth so snapshots are dated
within the correct month instead of today. For the current month, Date() is used.

Widget forward-fills missing month buckets (trend and category series) using the
most recent earlier month's value, preventing gaps when a check-in is done in the
following month.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

PortfolioJournal/Views/Dashboard/MonthlyCheckInView.swift

@@ -154,7 +154,8 @@ struct MonthlyCheckInView: View {
         .sheet(isPresented: $showBatchUpdate) {
             viewModel.refresh()
         } content: {
-            BatchUpdateView(sources: viewModel.sources)
+            let batchSaveDate = referenceDate.isSameMonth(as: Date()) ? Date() : referenceDate.endOfMonth
+            BatchUpdateView(sources: viewModel.sources, saveDate: batchSaveDate)
         }
         .onChange(of: starRating) { _, newValue in
             MonthlyCheckInStore.setRating(newValue == 0 ? nil : newValue, for: referenceDate)
@@ -945,10 +946,16 @@ struct AchievementMilestoneBar: View {
 struct BatchUpdateView: View {
     @Environment(\.dismiss) private var dismiss
     let sources: [InvestmentSource]
+    let saveDate: Date
     @State private var values: [UUID: String] = [:]
     @State private var contributions: [UUID: String] = [:]
     @State private var savedCount = 0
 
+    init(sources: [InvestmentSource], saveDate: Date = Date()) {
+        self.sources = sources
+        self.saveDate = saveDate
+    }
+
     var body: some View {
         NavigationStack {
             List {
@@ -1080,7 +1087,7 @@ struct BatchUpdateView: View {
 
             repository.createSnapshot(
                 for: source,
-                date: Date(),
+                date: saveDate,
                 value: parsed,
                 contribution: parsedContribution
             )

PortfolioJournalWidget/InvestmentWidget.swift

@@ -264,7 +264,12 @@ struct InvestmentWidgetProvider: TimelineProvider {
             }
             let monthFormatter = DateFormatter()
             monthFormatter.dateFormat = "MMM"
-            trendPoints = months.map { monthlyTotals[$0] ?? .zero }
+            trendPoints = months.map { month in
+                if let value = monthlyTotals[month] { return value }
+                // Forward-fill: use the most recent earlier month's value
+                let previous = sortedMonths.last { $0.0 < month }
+                return previous?.1 ?? .zero
+            }
             trendLabels = months.map { monthFormatter.string(from: $0) }
         }
 
@@ -307,7 +312,13 @@ struct InvestmentWidgetProvider: TimelineProvider {
 
         let categoryEvolution: [CategorySeries] = categoryTotalsData.prefix(4).map { category in
             let monthMap = categoryMonthlyTotals[category.id] ?? [:]
-            let points = months.map { monthMap[$0] ?? .zero }
+            let sortedCategoryMonths = monthMap.map { ($0.key, $0.value) }.sorted { $0.0 < $1.0 }
+            let points = months.map { month -> Decimal in
+                if let value = monthMap[month] { return value }
+                // Forward-fill: use the most recent earlier month's value
+                let previous = sortedCategoryMonths.last { $0.0 < month }
+                return previous?.1 ?? .zero
+            }
             return CategorySeries(
                 id: category.id,
                 name: category.name,