Charts: puntos + labels de valor en todas las gráficas de líneas

- Nuevo ChartValueLabels.swift: ChartValueBubble (cápsula) y ChartSelectionCard
  (tarjeta multi-serie), con umbral compartido (<=12 puntos → labels SIEMPRE
  visibles; las gráficas cortas aportan mucho más con los valores a la vista)
- PointMark añadido donde faltaba (Compare, Year vs Year, Drawdown, Volatility);
  agrandado donde ya existía (Evolution, Prediction, Period vs Period, Rolling)
- Selección por tap/arrastre (chartXSelection) en las 8 gráficas: RuleMark + burbuja
  prominente (una serie) o tarjeta con el valor de cada serie (multi-serie)
- Evolution reutiliza su scrubbing existente y ahora muestra burbuja en el punto
- Period vs Period: labels A arriba / B abajo para evitar solapes
- Drawdown/Volatility migrados de Chart(data:) a Chart{ForEach} para poder añadir
  marcas de selección

Verificado en iPad Pro 13" (labels visibles en Evolution y Period vs Period).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015qUZrBusG82T37R7PeokqJ

PortfolioJournal/Views/Charts/YearOverYearChartView.swift

@@ -3,6 +3,7 @@ import Charts
 
 struct YearOverYearChartView: View {
     @ObservedObject var viewModel: ChartsViewModel
+    @State private var selectedMonthIdx: Int?
 
     private let monthAbbreviations = ["Jan", "Feb", "Mar", "Apr", "May", "Jun",
                                       "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]
@@ -92,6 +93,18 @@ struct YearOverYearChartView: View {
 
     // MARK: - Chart
 
+    /// Two selected years × 12 months stays readable with permanent labels.
+    private var showAllLabels: Bool { selectedSeries.count <= 2 }
+
+    private func selectionRows(for month: Int) -> [(label: String, value: String, color: Color)] {
+        selectedSeries.compactMap { series in
+            let value = series.values[month]
+            guard !value.isNaN else { return nil }
+            let idx = allYears.firstIndex(where: { $0.id == series.id }) ?? 0
+            return (String(series.year), ChartLabels.percent(value), lineColors[idx % lineColors.count])
+        }
+    }
+
     @ViewBuilder
     private var chartBody: some View {
         if #available(iOS 16.0, *) {
@@ -99,6 +112,7 @@ struct YearOverYearChartView: View {
                 ForEach(selectedSeries) { yearSeries in
                     let idx = allYears.firstIndex(where: { $0.id == yearSeries.id }) ?? 0
                     let color = lineColors[idx % lineColors.count]
+                    let seriesPosition = selectedSeries.firstIndex(where: { $0.id == yearSeries.id }) ?? 0
                     ForEach(0..<12, id: \.self) { monthIdx in
                         let value = yearSeries.values[monthIdx]
                         if !value.isNaN {
@@ -109,10 +123,35 @@ struct YearOverYearChartView: View {
                             )
                             .foregroundStyle(color)
                             .interpolationMethod(.catmullRom)
+
+                            PointMark(
+                                x: .value("Month", monthIdx),
+                                y: .value("Return", value)
+                            )
+                            .foregroundStyle(color)
+                            .symbolSize(showAllLabels ? 32 : 18)
+                            .annotation(position: seriesPosition == 0 ? .top : .bottom, spacing: 2) {
+                                if showAllLabels {
+                                    ChartValueBubble(text: ChartLabels.percent(value), color: color)
+                                }
+                            }
                         }
                     }
                 }
+
+                if let selectedMonthIdx, selectedMonthIdx >= 0, selectedMonthIdx < 12 {
+                    RuleMark(x: .value("Selected", selectedMonthIdx))
+                        .foregroundStyle(Color.secondary.opacity(0.35))
+                        .lineStyle(StrokeStyle(lineWidth: 1, dash: [3, 3]))
+                        .annotation(position: .top, spacing: 4) {
+                            ChartSelectionCard(
+                                title: monthAbbreviations[selectedMonthIdx],
+                                rows: selectionRows(for: selectedMonthIdx)
+                            )
+                        }
+                }
             }
+            .chartXSelection(value: $selectedMonthIdx)
             .chartXAxis {
                 AxisMarks(values: Array(0..<12)) { value in
                     AxisValueLabel {