feat(template-engine): resolve TemplateEngine-002 — per-slot alarm override for derived templates

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.

src/ScadaLink.ConfigurationDatabase/Migrations/ScadaLinkDbContextModelSnapshot.cs

@@ -917,9 +917,15 @@ namespace ScadaLink.ConfigurationDatabase.Migrations
                         .HasMaxLength(2000)
                         .HasColumnType("nvarchar(2000)");
 
+                    b.Property<bool>("IsInherited")
+                        .HasColumnType("bit");
+
                     b.Property<bool>("IsLocked")
                         .HasColumnType("bit");
 
+                    b.Property<bool>("LockedInDerived")
+                        .HasColumnType("bit");
+
                     b.Property<string>("Name")
                         .IsRequired()
                         .HasMaxLength(200)