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/20260517000628_AddDerivedAlarmFields.cs

@@ -0,0 +1,40 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ScadaLink.ConfigurationDatabase.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddDerivedAlarmFields : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<bool>(
+                name: "IsInherited",
+                table: "TemplateAlarms",
+                type: "bit",
+                nullable: false,
+                defaultValue: false);
+
+            migrationBuilder.AddColumn<bool>(
+                name: "LockedInDerived",
+                table: "TemplateAlarms",
+                type: "bit",
+                nullable: false,
+                defaultValue: false);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "IsInherited",
+                table: "TemplateAlarms");
+
+            migrationBuilder.DropColumn(
+                name: "LockedInDerived",
+                table: "TemplateAlarms");
+        }
+    }
+}

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)