fix(client-ui): resolve Low code-review findings (Client.UI-003,004,006,009,010,011)

- Client.UI-003: wire Serilog properly per CLAUDE.md — console sink +
  rolling daily file sink in Program.Main, Log.CloseAndFlush in finally,
  per-VM Log.ForContext<> loggers.
- Client.UI-004: migrate the cert-store folder picker from the obsolete
  OpenFolderDialog to StorageProvider.OpenFolderPickerAsync (with
  TryGetFolderFromPathAsync seed + TryGetLocalPath extraction).
- Client.UI-006: surface formerly silent catch blocks via an observable
  StatusMessage on the Subscriptions / Alarms VMs that bubbles up into
  the shell's status bar; soft fallbacks log at Information level so
  hard failures stay distinguishable.
- Client.UI-009: docs/Client.UI.md now lists Standard Deviation in the
  Aggregate row of the Query Options table.
- Client.UI-010: removed the unused MinDateTimeProperty /
  MaxDateTimeProperty styled properties from DateTimeRangePicker.
- Client.UI-011: updated the cert-store TextBox watermark from the
  legacy AppData/LmxOpcUaClient/pki to the canonical
  AppData/OtOpcUaClient/pki.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/Controls/DateTimeRangePicker.axaml.cs

@@ -30,12 +30,6 @@ public partial class DateTimeRangePicker : UserControl
     public static readonly StyledProperty<string> EndTextProperty =
         AvaloniaProperty.Register<DateTimeRangePicker, string>(nameof(EndText), defaultValue: "");
 
-    public static readonly StyledProperty<DateTimeOffset?> MinDateTimeProperty =
-        AvaloniaProperty.Register<DateTimeRangePicker, DateTimeOffset?>(nameof(MinDateTime));
-
-    public static readonly StyledProperty<DateTimeOffset?> MaxDateTimeProperty =
-        AvaloniaProperty.Register<DateTimeRangePicker, DateTimeOffset?>(nameof(MaxDateTime));
-
     private bool _isUpdating;
 
     public DateTimeRangePicker()
@@ -67,18 +61,6 @@ public partial class DateTimeRangePicker : UserControl
         set => SetValue(EndTextProperty, value);
     }
 
-    public DateTimeOffset? MinDateTime
-    {
-        get => GetValue(MinDateTimeProperty);
-        set => SetValue(MinDateTimeProperty, value);
-    }
-
-    public DateTimeOffset? MaxDateTime
-    {
-        get => GetValue(MaxDateTimeProperty);
-        set => SetValue(MaxDateTimeProperty, value);
-    }
-
     protected override void OnLoaded(RoutedEventArgs e)
     {
         base.OnLoaded(e);