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

docs/requirements/Component-CentralUI.md

@@ -169,7 +169,7 @@ Central cluster only. Sites have no user interface.
   - **Source Reference** — the concrete native key for this instance.
   - **Filter** — the per-instance condition filter.
   - A **blank field inherits** the template default (the greyed placeholder shows the inherited value for context, mirroring the per-attribute Override field). **Save** and **Clear** act per row — Save persists the row's overrides, Clear reverts the row to the template-inherited binding. Locked template sources are not overridable.
-  - **Bulk retarget CSV import**: an `InputFile` upload on the card header accepts a CSV of `SourceName, Connection, SourceReference, Filter` rows — the same file format and batch rules as the CLI `instance native-alarm-source import --file` (see Component-CLI.md), parsed with the shared `NativeAlarmSourceOverrideCsvParser`. Each row is validated against the template's source bindings (name resolves, source not template-locked, no duplicate source in the file); the import is **all-or-nothing** — any error aborts the whole upload with a per-line error summary and nothing is applied. Semantics are **merge, not full replace**: sources absent from the file keep their existing override, a blank field keeps the inherited value, and a row with all three fields blank clears that source's override. On success the rows are upserted through the same repository path the inline Save uses.
+  - **Bulk retarget CSV import**: an `InputFile` upload on the card header accepts a CSV of `SourceName, Connection, SourceReference, Filter` rows, optionally followed by a `MesReportable` column (`true`/`false`/blank = inherit) — the same file format and batch rules as the CLI `instance native-alarm-source import --file` (see Component-CLI.md), parsed with the shared `NativeAlarmSourceOverrideCsvParser`. Each row is validated against the template's source bindings (name resolves, source not template-locked, no duplicate source in the file); the import is **all-or-nothing** — any error aborts the whole upload with a per-line error summary and nothing is applied. Semantics are **merge, not full replace**: sources absent from the file keep their existing override, a blank field keeps the inherited value, and a row with all three fields blank clears that source's override. A file without the `MesReportable` column leaves the MES flag unspecified, and the server keeps each source's stored MES override (`NativeAlarmSourceOverrideEntry.KeepStoredMesReportable`, #104) — the CLI import sends the same entries. On success the rows are upserted through the same repository path the inline Save uses.
 - Filter/search instances by site, area, template, or status.
 - **Disable** instances — stops data collection, script triggers, and alarm evaluation at the site while retaining the deployed configuration.
 - **Enable** instances — re-activates a disabled instance.