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/Views/MainWindow.axaml

@@ -78,7 +78,7 @@
                                     <TextBox Text="{Binding CertificateStorePath}"
                                              Width="370"
                                              IsReadOnly="True"
-                                             Watermark="(default: AppData/LmxOpcUaClient/pki)" />
+                                             Watermark="(default: AppData/OtOpcUaClient/pki)" />
                                     <Button Name="BrowseCertPathButton"
                                             Content="..."
                                             Width="30"