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/PredictionChartView.swift

@@ -4,6 +4,22 @@ import Charts
 struct PredictionChartView: View {
     let predictions: [Prediction]
     let historicalData: [(date: Date, value: Decimal)]
+    @State private var selectedDate: Date?
+
+    private var showAllLabels: Bool {
+        historicalData.count + predictions.count <= ChartLabels.alwaysShowThreshold
+    }
+
+    /// Nearest point (historical or predicted) to the selected date.
+    private var selectedPoint: (date: Date, value: Decimal, isPrediction: Bool)? {
+        guard let selectedDate else { return nil }
+        let all: [(date: Date, value: Decimal, isPrediction: Bool)] =
+            historicalData.map { ($0.date, $0.value, false) } +
+            predictions.map { ($0.date, $0.predictedValue, true) }
+        return all.min(by: {
+            abs($0.date.timeIntervalSince(selectedDate)) < abs($1.date.timeIntervalSince(selectedDate))
+        })
+    }
 
     var body: some View {
         VStack(alignment: .leading, spacing: 16) {
@@ -47,7 +63,12 @@ struct PredictionChartView: View {
                             y: .value("Value", NSDecimalNumber(decimal: item.value).doubleValue)
                         )
                         .foregroundStyle(Color.appPrimary)
-                        .symbolSize(24)
+                        .symbolSize(showAllLabels ? 36 : 24)
+                        .annotation(position: .top, spacing: 3) {
+                            if showAllLabels {
+                                ChartValueBubble(text: item.value.compactCurrencyString)
+                            }
+                        }
                     }
 
                     // Confidence interval area
@@ -74,7 +95,12 @@ struct PredictionChartView: View {
                             y: .value("Predicted", NSDecimalNumber(decimal: prediction.predictedValue).doubleValue)
                         )
                         .foregroundStyle(Color.appSecondary)
-                        .symbolSize(24)
+                        .symbolSize(showAllLabels ? 36 : 24)
+                        .annotation(position: .top, spacing: 3) {
+                            if showAllLabels {
+                                ChartValueBubble(text: prediction.predictedValue.compactCurrencyString, color: .appSecondary)
+                            }
+                        }
                     }
 
                     // Bull scenario line (upper confidence interval)
@@ -118,7 +144,27 @@ struct PredictionChartView: View {
                         .foregroundStyle(Color.appSecondary)
                         .lineStyle(StrokeStyle(lineWidth: 2, dash: [5, 5]))
                     }
+
+                    if let sel = selectedPoint {
+                        RuleMark(x: .value("Selected", sel.date))
+                            .foregroundStyle(Color.secondary.opacity(0.35))
+                            .lineStyle(StrokeStyle(lineWidth: 1, dash: [3, 3]))
+                        PointMark(
+                            x: .value("Selected", sel.date),
+                            y: .value("Value", NSDecimalNumber(decimal: sel.value).doubleValue)
+                        )
+                        .foregroundStyle(sel.isPrediction ? Color.appSecondary : Color.appPrimary)
+                        .symbolSize(80)
+                        .annotation(position: .top, spacing: 4) {
+                            ChartValueBubble(
+                                text: sel.value.compactCurrencyString,
+                                color: sel.isPrediction ? .appSecondary : .appPrimary,
+                                prominent: true
+                            )
+                        }
+                    }
                 }
+                .chartXSelection(value: $selectedDate)
                 .chartXAxis {
                     AxisMarks(values: .stride(by: .month, count: 3)) { value in
                         AxisValueLabel(format: .dateTime.month(.abbreviated).year(.twoDigits))