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/Services/ImportService.swift

@@ -383,6 +383,15 @@ Personal,Real Estate,Rental Property,2024-01-01,82000,80000,Estimated value
         let sourceRepository = InvestmentSourceRepository(context: context)
         let snapshotRepository = SnapshotRepository(context: context)
 
+        // Batch import: suppress the per-row widget refresh (each does a synchronous
+        // WAL checkpoint on the main context) to avoid hanging the main thread on
+        // large imports. Refresh once when everything is done.
+        CoreDataStack.shared.suppressWidgetRefresh = true
+        defer {
+            CoreDataStack.shared.suppressWidgetRefresh = false
+            CoreDataStack.shared.refreshWidgetData()
+        }
+
         var accountsCreated = 0
         var sourcesCreated = 0
         var snapshotsCreated = 0
@@ -475,7 +484,8 @@ Personal,Real Estate,Rental Property,2024-01-01,82000,80000,Estimated value
                                 date: snapshot.date,
                                 value: snapshot.value,
                                 contribution: snapshot.contribution,
-                                notes: snapshot.notes
+                                notes: snapshot.notes,
+                                batch: true
                             )
                             snapshotsCreated += 1
                         }