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/ViewModels/EntryEditViewModel.swift

@@ -1,8 +1,4 @@
-//
-//  EntryEditViewModel.swift
-//  MyPass
-//
-
+// MyPass/ViewModels/EntryEditViewModel.swift
 import Foundation
 import Combine
 import SwiftUI
@@ -16,16 +12,17 @@ final class EntryEditViewModel: ObservableObject {
     @Published var url: String
     @Published var notes: String
     @Published var customFields: [CustomField]
+    @Published var groupId: UUID
     @Published var errorMessage: String?
     @Published var isSaving: Bool = false
 
-    private let session: VaultSession
-    private let groupId: UUID?
+    let session: VaultSession
     private let existingEntry: Entry?
 
-    /// `groupId` is required when adding a new entry, and unused when editing an existing one
-    /// (an existing entry's group is looked up internally by `VaultSession.updateEntry`).
-    init(session: VaultSession, groupId: UUID? = nil, existing: Entry? = nil) {
+    /// `groupId` is the target group for a new entry, or the entry's current group when
+    /// editing (shown read-only in that case -- MyPass doesn't support re-parenting an
+    /// existing entry to a different group yet).
+    init(session: VaultSession, groupId: UUID, existing: Entry? = nil) {
         self.session = session
         self.groupId = groupId
         self.existingEntry = existing
@@ -39,6 +36,11 @@ final class EntryEditViewModel: ObservableObject {
 
     var isEditing: Bool { existingEntry != nil }
 
+    var flatGroups: [FlatGroup] {
+        guard let root = session.database?.root else { return [] }
+        return flattenGroups(in: root)
+    }
+
     func save(dismiss: @escaping () -> Void) {
         Task {
             isSaving = true
@@ -53,11 +55,6 @@ final class EntryEditViewModel: ObservableObject {
                     entry.customFields = customFields
                     try session.updateEntry(entry)
                 } else {
-                    guard let groupId else {
-                        errorMessage = "No group selected for the new entry."
-                        isSaving = false
-                        return
-                    }
                     let entry = Entry(
                         title: title,
                         username: username,