feat: move test buttons to right panel, add user auth dialog for reports

Move Start/Stop/Report buttons from the middle panel to the top of
TestPanelView (automated tests section), matching the old application
layout. Remove inline Operator/Client text fields — operator identity
now comes from a UserCheckDialog (username/password) shown before the
existing ReportDialog. Add credential storage to ConfigurationService.

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

Views/Dialogs/UserCheckDialog.xaml

@@ -0,0 +1,43 @@
+<Window x:Class="HC_APTBS.Views.Dialogs.UserCheckDialog"
+        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+        mc:Ignorable="d"
+        Title="User Authentication"
+        Height="170" Width="420"
+        ResizeMode="NoResize"
+        WindowStartupLocation="CenterOwner">
+
+    <Grid Margin="16,12">
+        <Grid.RowDefinitions>
+            <RowDefinition Height="Auto"/>
+            <RowDefinition Height="Auto"/>
+            <RowDefinition Height="Auto"/>
+        </Grid.RowDefinitions>
+        <Grid.ColumnDefinitions>
+            <ColumnDefinition Width="90"/>
+            <ColumnDefinition/>
+        </Grid.ColumnDefinitions>
+
+        <!-- Username -->
+        <Label Content="Username:" VerticalAlignment="Center" HorizontalAlignment="Right"/>
+        <TextBox Grid.Column="1" Margin="8,4" Height="26" VerticalContentAlignment="Center"
+                 Text="{Binding Username, UpdateSourceTrigger=PropertyChanged}"/>
+
+        <!-- Password -->
+        <Label Grid.Row="1" Content="Password:" VerticalAlignment="Center" HorizontalAlignment="Right"/>
+        <PasswordBox x:Name="PBPassword" Grid.Row="1" Grid.Column="1"
+                     Margin="8,4" Height="26" VerticalContentAlignment="Center"
+                     PasswordChanged="OnPasswordChanged"/>
+
+        <!-- Buttons -->
+        <StackPanel Grid.Row="2" Grid.Column="1"
+                    Orientation="Horizontal" HorizontalAlignment="Right" Margin="0,12,0,0">
+            <Button Content="Accept" Width="80" Height="26" Margin="0,0,8,0"
+                    Command="{Binding AcceptCommand}" IsDefault="True"/>
+            <Button Content="Cancel" Width="80" Height="26"
+                    Command="{Binding CancelCommand}" IsCancel="True"/>
+        </StackPanel>
+    </Grid>
+</Window>