Fix sync iCloud del Goal: accessor nil-tolerante en createdAt (Goal/Account/InvestmentSource)

El modelo declara createdAt optional=YES pero las clases lo tenían @NSManaged var createdAt: Date
(no-opcional). Al materializar un registro importado por CloudKit con createdAt transitoriamente
nil, el acceso revienta el merge → contribuye al CKErrorPartialFailure y a que el Goal no sincronice.
Mismo patrón safeValue/setManagedValue ya aplicado a Snapshot (hotfix b76b8f8) que no cubrió estas 3.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LZFmGhbWzibhApev3C4554

PortfolioJournal/Models/CoreData/Account+CoreDataClass.swift

@@ -15,7 +15,13 @@ public class Account: NSManagedObject, Identifiable {
         get { safeValue(forKey: "name", fallback: "") }
         set { setManagedValue(newValue, forKey: "name") }
     }
-    @NSManaged public var createdAt: Date
+    // createdAt is optional in the model; a non-optional @NSManaged Date crashes the
+    // CloudKit merge when an imported record materialises with a transient nil.
+    // Same nil-tolerant accessor pattern already applied to Snapshot.
+    @objc public var createdAt: Date {
+        get { safeValue(forKey: "createdAt", fallback: .distantPast) }
+        set { setManagedValue(newValue, forKey: "createdAt") }
+    }
     @NSManaged public var currency: String?
     @NSManaged public var inputMode: String
     @NSManaged public var notificationFrequency: String

PortfolioJournal/Models/CoreData/Goal+CoreDataClass.swift

@@ -18,7 +18,13 @@ public class Goal: NSManagedObject, Identifiable {
     @NSManaged public var targetAmount: NSDecimalNumber?
     @NSManaged public var targetDate: Date?
     @NSManaged public var isActive: Bool
-    @NSManaged public var createdAt: Date
+    // createdAt is optional in the model; a non-optional @NSManaged Date crashes the
+    // CloudKit merge when an imported record materialises with a transient nil.
+    // Same nil-tolerant accessor pattern already applied to Snapshot.
+    @objc public var createdAt: Date {
+        get { safeValue(forKey: "createdAt", fallback: .distantPast) }
+        set { setManagedValue(newValue, forKey: "createdAt") }
+    }
     @NSManaged public var account: Account?
 
     public override func awakeFromInsert() {

PortfolioJournal/Models/CoreData/InvestmentSource+CoreDataClass.swift

@@ -19,7 +19,13 @@ public class InvestmentSource: NSManagedObject, Identifiable {
     @NSManaged public var customFrequencyMonths: Int16
     @NSManaged public var isActive: Bool
     @NSManaged public var monthlyContribution: NSDecimalNumber?
-    @NSManaged public var createdAt: Date
+    // createdAt is optional in the model; a non-optional @NSManaged Date crashes the
+    // CloudKit merge when an imported record materialises with a transient nil.
+    // Same nil-tolerant accessor pattern already applied to Snapshot.
+    @objc public var createdAt: Date {
+        get { safeValue(forKey: "createdAt", fallback: .distantPast) }
+        set { setManagedValue(newValue, forKey: "createdAt") }
+    }
     @NSManaged public var category: Category?
     @NSManaged public var account: Account?
     @NSManaged public var snapshots: NSSet?