feat(alarms): HiLo trigger type with per-band level, hysteresis, messages, overrides

Adds a new HiLo alarm trigger type with four configurable setpoints
(LoLo / Lo / Hi / HiHi). Each setpoint carries an optional priority,
deadband (for hysteresis), and operator message. The site runtime emits
AlarmStateChanged with an AlarmLevel field so consumers can differentiate
warning vs critical bands.

Plumbing:
  - new AlarmLevel enum + AlarmStateChanged.Level/Message init properties
  - AlarmTriggerEditor (Blazor) gets a HiLo render with severity tinting
  - AlarmTriggerConfigCodec extracted from the editor for testability
  - sitestream.proto carries level + message over gRPC
  - SemanticValidator enforces numeric attribute, setpoint ordering,
    non-negative deadband
  - on-trigger scripts get an Alarm global (Name/Level/Priority/Message)
    so notification routing can branch by severity
  - per-instance InstanceAlarmOverride entity + EF migration + flattening
    step + CLI commands; HiLo overrides merge setpoint-by-setpoint, binary
    types whole-replace
  - DebugView shows a Level badge + per-band message tooltip
  - App.razor auto-reloads on permanent Blazor circuit failure
  - docker/regen-proto.sh automates the proto regen workflow (the linux/arm64
    protoc segfault means generated files are checked in for now)

src/ScadaLink.ConfigurationDatabase/Migrations/ScadaLinkDbContextModelSnapshot.cs

@@ -478,6 +478,37 @@ namespace ScadaLink.ConfigurationDatabase.Migrations
                     b.ToTable("Instances");
                 });
 
+            modelBuilder.Entity("ScadaLink.Commons.Entities.Instances.InstanceAlarmOverride", b =>
+                {
+                    b.Property<int>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("int");
+
+                    SqlServerPropertyBuilderExtensions.UseIdentityColumn(b.Property<int>("Id"));
+
+                    b.Property<string>("AlarmCanonicalName")
+                        .IsRequired()
+                        .HasMaxLength(400)
+                        .HasColumnType("nvarchar(400)");
+
+                    b.Property<int>("InstanceId")
+                        .HasColumnType("int");
+
+                    b.Property<int?>("PriorityLevelOverride")
+                        .HasColumnType("int");
+
+                    b.Property<string>("TriggerConfigurationOverride")
+                        .HasMaxLength(4000)
+                        .HasColumnType("nvarchar(4000)");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("InstanceId", "AlarmCanonicalName")
+                        .IsUnique();
+
+                    b.ToTable("InstanceAlarmOverrides");
+                });
+
             modelBuilder.Entity("ScadaLink.Commons.Entities.Instances.InstanceAttributeOverride", b =>
                 {
                     b.Property<int>("Id")
@@ -1144,6 +1175,15 @@ namespace ScadaLink.ConfigurationDatabase.Migrations
                         .IsRequired();
                 });
 
+            modelBuilder.Entity("ScadaLink.Commons.Entities.Instances.InstanceAlarmOverride", b =>
+                {
+                    b.HasOne("ScadaLink.Commons.Entities.Instances.Instance", null)
+                        .WithMany("AlarmOverrides")
+                        .HasForeignKey("InstanceId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+                });
+
             modelBuilder.Entity("ScadaLink.Commons.Entities.Instances.InstanceAttributeOverride", b =>
                 {
                     b.HasOne("ScadaLink.Commons.Entities.Instances.Instance", null)
@@ -1271,6 +1311,8 @@ namespace ScadaLink.ConfigurationDatabase.Migrations
 
             modelBuilder.Entity("ScadaLink.Commons.Entities.Instances.Instance", b =>
                 {
+                    b.Navigation("AlarmOverrides");
+
                     b.Navigation("AttributeOverrides");
 
                     b.Navigation("ConnectionBindings");