fix: migrate legacy backups missing wallet id on restore

Backups written before activity data became wallet-scoped have no wallet id on
their activity, tag and pre-activity-metadata records. With bitkit-core 0.4.0
those records require a wallet id, so decoding such a backup throws before the
records reach Core.

Before decoding a restored envelope, hand each Core-owned array to the matching
bitkit-core migration helper (migrateBackupActivitiesJson,
migrateBackupActivityTagsJson, migrateBackupPreActivityMetadataJson), which
fills in the default wallet id for records that lack one and preserves any
existing id. The app never edits Core model JSON itself, and current backups
that already carry a wallet id are unaffected.

Bumps bitkit-core to 0.4.0.

Author: coreyphillips

Bitkit.xcodeproj/project.pbxproj

@@ -1201,7 +1201,7 @@
 			repositoryURL = "https://github.com/synonymdev/bitkit-core";
 			requirement = {
 				kind = exactVersion;
-				version = 0.3.9;
+				version = 0.4.0;
 			};
 		};
 		96E20CD22CB6D91A00C24149 /* XCRemoteSwiftPackageReference "CodeScanner" */ = {

Bitkit.xcodeproj/project.xcworkspace/xcshareddata/swiftpm/Package.resolved

@@ -211,7 +211,11 @@ class BackupService {
             }
 
             try await performRestore(category: .activity) { dataBytes in
-                let payload = try JSONDecoder().decode(ActivityBackupV1.self, from: dataBytes)
+                let migrated = try self.migrateCoreOwnedBackupFields(dataBytes, fieldMigrations: [
+                    "activities": migrateBackupActivitiesJson,
+                    "activityTags": migrateBackupActivityTagsJson,
+                ])
+                let payload = try JSONDecoder().decode(ActivityBackupV1.self, from: migrated)
 
                 try await CoreService.shared.activity.upsertList(payload.activities)
                 try await CoreService.shared.activity.upsertTags(payload.activityTags)
@@ -224,7 +228,10 @@ class BackupService {
             }
 
             try await performRestore(category: .metadata) { dataBytes in
-                let payload = try JSONDecoder().decode(MetadataBackupV1.self, from: dataBytes)
+                let migrated = try self.migrateCoreOwnedBackupFields(dataBytes, fieldMigrations: [
+                    "tagMetadata": migrateBackupPreActivityMetadataJson,
+                ])
+                let payload = try JSONDecoder().decode(MetadataBackupV1.self, from: migrated)
 
                 try await CoreService.shared.activity.upsertPreActivityMetadata(payload.tagMetadata)
 
@@ -739,6 +746,28 @@ class BackupService {
         }
     }
 
+    /// Fills in wallet ids that predate wallet-scoped activity data before a
+    /// backup envelope is decoded. Each Core-owned array field is handed to the
+    /// matching Core migration helper as raw JSON, so the app never edits Core
+    /// model JSON itself. Records that already carry a wallet id are left
+    /// unchanged, so this is safe to run on current backups too.
+    private func migrateCoreOwnedBackupFields(
+        _ dataBytes: Data,
+        fieldMigrations: [String: (String) throws -> String]
+    ) throws -> Data {
+        guard var root = try JSONSerialization.jsonObject(with: dataBytes) as? [String: Any] else {
+            return dataBytes
+        }
+        for (field, migrate) in fieldMigrations {
+            guard let array = root[field] as? [Any] else { continue }
+            let arrayData = try JSONSerialization.data(withJSONObject: array)
+            let migratedJson = try migrate(String(decoding: arrayData, as: UTF8.self))
+            guard let migratedData = migratedJson.data(using: .utf8) else { continue }
+            root[field] = try JSONSerialization.jsonObject(with: migratedData)
+        }
+        return try JSONSerialization.data(withJSONObject: root)
+    }
+
     private func performRestore(category: BackupCategory, restoreAction: (Data) async throws -> Void) async throws {
         do {
             let item = try await vssBackupClient.getObject(key: category.rawValue)