Adds IsInherited/LockedInDerived to the TemplateAlarm entity (mirroring the
attribute/script override model), an EF migration, base-alarm copy-on-derive,
inherited-alarm flattening skip, and LockedInDerived override-rejection validation.
FlatteningService now treats IsInherited rows as placeholders: when a
derived template carries an inherited attribute or script, the live base
value resolves through the ParentTemplateId chain instead of the
(possibly stale) copy. An IsInherited=false row is a real override and
wins as before.
ValidateLockedInDerived runs once per chain (main + composed) and returns
a flatten-time failure if a derived template overrides a base row that
the base marked LockedInDerived.
TemplateService.Update{Attribute,Script}Async reject mid-flight when a
derived target tries to override a LockedInDerived base member, and now
persist IsInherited/LockedInDerived from the proposed payload so the UI
can flip override state or set base-locks via the same endpoints.
Replace SiteDataConnectionAssignment join table with a direct SiteId FK on DataConnection,
simplifying the data model, repositories, UI, CLI, and deployment service.
