Fix ANR al terminar el import CSV (save + widget refresh por cada fila)

createSnapshot hacía save() por cada snapshot, y save() dispara refreshWidgetData
→ checkpointWAL (performAndWait en el viewContext main) + reloadAllTimelines. Con
213 snapshots eran 213 saves + 213 checkpoints en el main → Application Not
Responding. Añadido modo batch a createSnapshot (no guarda por fila; applyImport
ya guarda el contexto una vez al final) y flag suppressWidgetRefresh en
CoreDataStack para neutralizar el refresh por fila durante el import, con un único
refreshWidgetData al terminar.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01L2p3gUZRNWW388rWFRjiU7

PortfolioJournal/Models/CoreDataStack.swift

@@ -772,7 +772,14 @@ class CoreDataStack: ObservableObject {
 
     // MARK: - Widget Data Refresh
 
+    /// When true, `refreshWidgetData()` becomes a no-op. Set during batch operations
+    /// (e.g. CSV import of hundreds of snapshots) so we don't run a synchronous WAL
+    /// checkpoint + widget reload per row — that hammered the main thread into an ANR.
+    /// Call `refreshWidgetData()` once when the batch finishes.
+    var suppressWidgetRefresh = false
+
     func refreshWidgetData() {
+        if suppressWidgetRefresh { return }
         if #available(iOS 14.0, *) {
             if Self.appGroupEnabled {
                 checkpointWAL()