feat: require groupId in EntryEditViewModel, add group picker to EntryEditView

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WYqycDFsynHH9VnnK7LNSf

MyPass/Views/EntryEditView.swift

@@ -1,8 +1,4 @@
-//
-//  EntryEditView.swift
-//  MyPass
-//
-
+// MyPass/Views/EntryEditView.swift
 import SwiftUI
 import MyPassCore
 
@@ -13,6 +9,16 @@ struct EntryEditView: View {
     var body: some View {
         NavigationStack {
             Form {
+                if !vm.isEditing {
+                    Section("Group") {
+                        Picker("Group", selection: $vm.groupId) {
+                            ForEach(vm.flatGroups) { flatGroup in
+                                Text(groupLabel(for: flatGroup)).tag(flatGroup.group.id)
+                            }
+                        }
+                    }
+                }
+
                 Section("Credentials") {
                     TextField("Title", text: $vm.title)
                     TextField("Username", text: $vm.username)
@@ -69,4 +75,8 @@ struct EntryEditView: View {
             }
         }
     }
+
+    private func groupLabel(for flatGroup: FlatGroup) -> String {
+        (flatGroup.breadcrumb.map(\.name) + [flatGroup.group.name]).joined(separator: " > ")
+    }
 }