fix(native-alarms): a 4-column CSV import keeps stored MES overrides on the CLI path too (ScadaBridge#104)

The bulk SetInstanceNativeAlarmSourceOverridesCommand handler always wrote the
entry's IsMesReportableOverride, so a CLI import of a legacy 4-column CSV (no
MesReportable column) reset every imported source's MES override to inherit. The
Central UI avoided it only by looking up the stored flag client-side.

NativeAlarmSourceOverrideEntry gains an additive trailing KeepStoredMesReportable
flag: when set, the server leaves an existing row's MES override untouched (a new
row inherits) and ignores IsMesReportableOverride; unset keeps the old meaning
(null = clear to inherit), so older senders are unaffected. The CLI and the Central
UI now build their entries through one rule (ToOverrideEntry on each row type):
no MesReportable column => KeepStoredMesReportable. CLI README and
Component-CentralUI updated.

Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV

src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Deployment/InstanceConfigure.razor

@@ -1885,11 +1885,7 @@
             }
 
             await MutationServices.ExecuteConfigurationAsync(new SetInstanceNativeAlarmSourceOverridesCommand(Id,
-                outcome.Rows.Select(row => new NativeAlarmSourceOverrideEntry(row.SourceName, row.Connection, row.SourceReference, row.Filter,
-                    // A file with the MesReportable column is authoritative; a legacy 4-column file keeps the stored flag.
-                    row.HasMesColumn
-                        ? row.MesReportable
-                        : _existingNativeOverrides.GetValueOrDefault(row.SourceName)?.IsMesReportableOverride)).ToList()));
+                outcome.Rows.Select(row => row.ToOverrideEntry()).ToList()));
             await OnInitializedAsync();
 
             _nasCsvImportSucceeded = true;