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.SiteRuntime/Scripts/ScriptCompilationService.cs

@@ -181,6 +181,14 @@ public class ScriptGlobals
     public ScriptParameters Parameters { get; set; } = new ScriptParameters();
     public CancellationToken CancellationToken { get; set; }
 
+    /// <summary>
+    /// Alarm context when this script is invoked as an on-trigger handler.
+    /// Null for instance scripts, shared scripts, and inbound-API-routed
+    /// scripts. Lets on-trigger scripts read the firing alarm's Name, Level
+    /// (HiLo only), Priority, and per-band Message to branch routing logic.
+    /// </summary>
+    public Commons.Types.Scripts.AlarmContext? Alarm { get; set; }
+
     /// <summary>
     /// Where this script sits in the composition tree. Defaults to root for
     /// scripts on top-level templates; a flattened composed script gets