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/ComparisonChartView.swift

@@ -2,6 +2,14 @@ import SwiftUI
 import Charts
 
 struct ComparisonChartView: View {
+    @State private var selectedDate: Date?
+
+    private static let selectionDateFormatter: DateFormatter = {
+        let f = DateFormatter()
+        f.dateFormat = "MMM yyyy"
+        return f
+    }()
+
     @ObservedObject var viewModel: ChartsViewModel
 
 
@@ -102,6 +110,21 @@ struct ComparisonChartView: View {
             .frame(height: 260)
     }
 
+    /// Permanent labels only when the chart stays readable (few points AND few series).
+    private var showAllLabels: Bool {
+        let maxPoints = viewModel.comparisonData.map { $0.points.count }.max() ?? 0
+        return maxPoints <= ChartLabels.alwaysShowThreshold && viewModel.comparisonData.count <= 3
+    }
+
+    private func selectionRows(for date: Date) -> [(label: String, value: String, color: Color)] {
+        viewModel.comparisonData.compactMap { series in
+            guard let point = series.points.min(by: {
+                abs($0.date.timeIntervalSince(date)) < abs($1.date.timeIntervalSince(date))
+            }) else { return nil }
+            return (series.name, yAxisLabel(for: point.value), Color(hex: series.colorHex) ?? .appPrimary)
+        }
+    }
+
     private var lineChart: some View {
         VStack(spacing: 12) {
             Chart {
@@ -115,9 +138,34 @@ struct ComparisonChartView: View {
                         )
                         .foregroundStyle(seriesColor)
                         .interpolationMethod(.catmullRom)
+
+                        PointMark(
+                            x: .value("Date", point.date),
+                            y: .value("Value", point.value)
+                        )
+                        .foregroundStyle(seriesColor)
+                        .symbolSize(showAllLabels ? 32 : 16)
+                        .annotation(position: .top, spacing: 2) {
+                            if showAllLabels {
+                                ChartValueBubble(text: yAxisLabel(for: point.value), color: seriesColor)
+                            }
+                        }
                     }
                 }
+
+                if let selectedDate {
+                    RuleMark(x: .value("Selected", selectedDate))
+                        .foregroundStyle(Color.secondary.opacity(0.35))
+                        .lineStyle(StrokeStyle(lineWidth: 1, dash: [3, 3]))
+                        .annotation(position: .top, spacing: 4) {
+                            ChartSelectionCard(
+                                title: Self.selectionDateFormatter.string(from: selectedDate),
+                                rows: selectionRows(for: selectedDate)
+                            )
+                        }
+                }
             }
+            .chartXSelection(value: $selectedDate)
             .chartXAxis {
                 AxisMarks(values: .stride(by: .month, count: xAxisStride)) { value in
                     AxisGridLine(stroke: StrokeStyle(lineWidth: 0.5, dash: [3, 3]))