Fix compilation errors in ChartsViewModel and AllocationEvolutionChart

- Remove unnecessary optional binding for non-optional source.id
- Break up AllocationEvolutionChart body to help Swift type-checker

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

PortfolioJournal/ViewModels/ChartsViewModel.swift

@@ -294,8 +294,7 @@ class ChartsViewModel: ObservableObject {
         let sources: [InvestmentSource]
         if !selectedSourceIds.isEmpty {
             sources = sourceRepository.sources.filter { source in
-                guard let id = source.id else { return false }
-                return selectedSourceIds.contains(id) && shouldIncludeSource(source)
+                selectedSourceIds.contains(source.id) && shouldIncludeSource(source)
             }
         } else if let selectedSource {
             sources = sourceRepository.sources.filter { $0.id == selectedSource.id && shouldIncludeSource($0) }

PortfolioJournal/Views/Charts/ChartsContainerView.swift

@@ -929,28 +929,60 @@ struct CashflowStackedChartView: View {
 
 // MARK: - Allocation Evolution Chart
 
+struct AllocationEvolutionDataPoint: Identifiable {
+    let id: String
+    let date: Date
+    let category: String
+    let percentage: Double
+    let color: String
+}
+
 struct AllocationEvolutionChart: View {
     let data: [(date: Date, category: String, percentage: Double, color: String)]
 
+    private var identifiableData: [AllocationEvolutionDataPoint] {
+        data.enumerated().map { index, item in
+            AllocationEvolutionDataPoint(
+                id: "\(index)-\(item.category)",
+                date: item.date,
+                category: item.category,
+                percentage: item.percentage,
+                color: item.color
+            )
+        }
+    }
+
     var body: some View {
         VStack(alignment: .leading, spacing: 12) {
             Text("Allocation Over Time")
                 .font(.headline)
 
             if data.isEmpty {
+                emptyView
+            } else {
+                chartView
+            }
+        }
+        .padding()
+        .background(Color(.systemBackground))
+        .cornerRadius(AppConstants.UI.cornerRadius)
+        .shadow(color: .black.opacity(0.05), radius: 8, y: 2)
+    }
+
+    private var emptyView: some View {
         Text("Not enough data to show allocation evolution.")
             .foregroundColor(.secondary)
             .frame(height: 260)
-            } else {
-                Chart {
-                    ForEach(data, id: \.date.description + \.category) { item in
+    }
+
+    private var chartView: some View {
+        Chart(identifiableData) { item in
             AreaMark(
                 x: .value("Date", item.date),
                 y: .value("Percentage", item.percentage)
             )
             .foregroundStyle(by: .value("Category", item.category))
         }
-                }
         .chartForegroundStyleScale(domain: categoryNames, range: categoryColors)
         .chartXAxis {
             AxisMarks(values: .stride(by: .month, count: 2)) { _ in
@@ -970,12 +1002,6 @@ struct AllocationEvolutionChart: View {
         .frame(height: 260)
         .drawingGroup()
     }
-        }
-        .padding()
-        .background(Color(.systemBackground))
-        .cornerRadius(AppConstants.UI.cornerRadius)
-        .shadow(color: .black.opacity(0.05), radius: 8, y: 2)
-    }
 
     private var categoryNames: [String] {
         Array(Set(data.map { $0.category })).sorted()