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.Communication/ScadaLink.Communication.csproj

@@ -30,4 +30,21 @@
     <ProjectReference Include="../ScadaLink.HealthMonitoring/ScadaLink.HealthMonitoring.csproj" />
   </ItemGroup>
 
+  <!-- gRPC proto generation. The compiled C# is checked in under
+       SiteStreamGrpc/ (Sitestream.cs + SitestreamGrpc.cs) because protoc
+       segfaults inside our linux_arm64 Docker build image. To regenerate
+       after schema changes:
+         1. Temporarily uncomment the Protobuf ItemGroup below.
+         2. Delete SiteStreamGrpc/*.cs.
+         3. `dotnet build` (on macOS) — Grpc.Tools writes fresh files to obj/.
+         4. Copy obj/Debug/net10.0/Protos/*.cs into SiteStreamGrpc/.
+         5. Re-comment the ItemGroup.
+       Eventually we should switch the Docker build image to one with a
+       working protoc on arm64. -->
+  <!--
+    <ItemGroup>
+    <Protobuf Include="Protos\sitestream.proto" GrpcServices="Both" />
+  </ItemGroup>
+  -->
+
 </Project>