feat: page-based navigation shell + Tests page wizard

Replace the monolithic MainWindow with a SelectedPage-driven shell
(Dashboard / Pump / Bench / Tests / Results / Settings). The Tests
page gets the Plan -> Preconditions -> Running -> Done wizard from
ui-structure.md \u00a74, backed by a 7-item precondition gate and
shared sub-views (PhaseCardView / TestSectionView / GraphicIndicatorView)
extracted from the now-deleted monolithic TestPanelView.

New VMs / views:
- Tests wizard: TestPreconditions, PhaseCard, GraphicIndicator,
  TestSection, TestPlan, TestRunning, TestDone
- Dashboard panels: DashboardConnection, DashboardReadings,
  DashboardAlarms, InterlockBanner, ResultHistory
- Pump / bench panels: PumpIdentificationPanel, PumpLiveData,
  UnlockPanel, BenchDriveControl, BenchReadings, RelayBank,
  TemperatureControl, DtcList, AuthGate
- Dialogs: generic ConfirmDialog, UserManageDialog, UserPromptDialog

Supporting changes:
- IsOilPumpOn exposed on MainViewModel for precondition evaluation
- RequiresAuth added to TestDefinition (XML round-trip)
- BipStatusDefinition + CompletedTestRun models
- ~35 new Test.* localization keys (en + es)
- Settings moved from modal dialog to full page
- Pause / Retry / Skip stubs in TestRunningView; full spec in
  docs/gap-test-running-controls.md for follow-up implementation
- docs/ui-structure.md captures the wizard design

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Views/Dialogs/UserPromptDialog.xaml.cs

@@ -0,0 +1,59 @@
+using System.Windows;
+
+namespace HC_APTBS.Views.Dialogs
+{
+    /// <summary>
+    /// Small input dialog that prompts for a username and password, or a password only.
+    /// Used by <see cref="Views.Dialogs.UserManageDialog"/> when adding a new user or
+    /// changing an existing user's password. Kept as a code-behind dialog (not MVVM)
+    /// because it is a transient prompt with no shared state.
+    /// </summary>
+    public partial class UserPromptDialog : Window
+    {
+        /// <summary>Username entered by the operator. Empty when <see cref="UsernameVisible"/> is false.</summary>
+        public string EnteredUsername { get; private set; } = string.Empty;
+
+        /// <summary>Password entered by the operator.</summary>
+        public string EnteredPassword { get; private set; } = string.Empty;
+
+        /// <summary>
+        /// Creates the dialog.
+        /// </summary>
+        /// <param name="title">Window title (already-localised string).</param>
+        /// <param name="usernameVisible">
+        /// True to show the username field (Add user flow); false to hide it (Change password flow).
+        /// </param>
+        /// <param name="prefillUsername">
+        /// Pre-filled, read-only username shown as a label when <paramref name="usernameVisible"/> is false.
+        /// Ignored otherwise.
+        /// </param>
+        public UserPromptDialog(string title, bool usernameVisible, string prefillUsername = "")
+        {
+            InitializeComponent();
+            Title = title;
+
+            if (usernameVisible)
+            {
+                EnteredUsername = string.Empty;
+                TbUsername.Focus();
+            }
+            else
+            {
+                // Hide username row; reserve width so layout doesn't shift.
+                LblUsername.Visibility = Visibility.Collapsed;
+                TbUsername.Visibility = Visibility.Collapsed;
+                EnteredUsername = prefillUsername;
+                PbPassword.Focus();
+            }
+        }
+
+        private void OnAccept(object sender, RoutedEventArgs e)
+        {
+            if (TbUsername.Visibility == Visibility.Visible)
+                EnteredUsername = TbUsername.Text;
+            EnteredPassword = PbPassword.Password;
+            DialogResult = true;
+            Close();
+        }
+    }
+}