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.CentralUI/Components/Pages/Deployment/DebugView.razor

@@ -191,6 +191,7 @@
                                     <tr>
                                         <th>Alarm</th>
                                         <th>State</th>
+                                        <th>Level</th>
                                         <th>Priority</th>
                                         <th>Timestamp</th>
                                     </tr>
@@ -198,12 +199,30 @@
                                 <tbody aria-live="polite" aria-atomic="false">
                                     @foreach (var alarm in FilteredAlarmStates)
                                     {
-                                        <tr class="@GetAlarmRowClass(alarm.State)">
-                                            <td class="small">@alarm.AlarmName</td>
+                                        <tr class="@GetAlarmRowClass(alarm.State)"
+                                            title="@(string.IsNullOrEmpty(alarm.Message) ? null : alarm.Message)">
+                                            <td class="small">
+                                                @alarm.AlarmName
+                                                @if (!string.IsNullOrEmpty(alarm.Message))
+                                                {
+                                                    <span class="ms-1 text-info" aria-label="Has operator message">💬</span>
+                                                }
+                                            </td>
                                             <td>
                                                 <span class="badge @GetAlarmStateBadge(alarm.State)"
                                                       aria-label="@($"Alarm state: {alarm.State}")">@alarm.State</span>
                                             </td>
+                                            <td>
+                                                @if (alarm.Level != AlarmLevel.None)
+                                                {
+                                                    <span class="badge @GetAlarmLevelBadge(alarm.Level)"
+                                                          aria-label="@($"Alarm level: {alarm.Level}")">@FormatLevel(alarm.Level)</span>
+                                                }
+                                                else
+                                                {
+                                                    <span class="text-muted small">—</span>
+                                                }
+                                            </td>
                                             <td class="small">@alarm.Priority</td>
                                             <td class="small text-muted"
                                                 title="@alarm.Timestamp.LocalDateTime.ToString("HH:mm:ss.fff")">
@@ -468,6 +487,26 @@
         _ => ""
     };
 
+    /// <summary>
+    /// Severity-tinted badge class for HiLo alarm levels. The critical bands
+    /// (HighHigh / LowLow) get the danger class; warning bands get amber.
+    /// </summary>
+    private static string GetAlarmLevelBadge(AlarmLevel level) => level switch
+    {
+        AlarmLevel.HighHigh or AlarmLevel.LowLow => "bg-danger",
+        AlarmLevel.High or AlarmLevel.Low => "bg-warning text-dark",
+        _ => "bg-secondary"
+    };
+
+    private static string FormatLevel(AlarmLevel level) => level switch
+    {
+        AlarmLevel.HighHigh => "HiHi",
+        AlarmLevel.High => "Hi",
+        AlarmLevel.Low => "Lo",
+        AlarmLevel.LowLow => "LoLo",
+        _ => "—"
+    };
+
     public void Dispose()
     {
         if (_session != null)

src/ScadaLink.CentralUI/Components/Pages/Design/TemplateEdit.razor

@@ -754,7 +754,8 @@
                                     <AlarmTriggerEditor TriggerType="@_alarmTriggerType"
                                                         Value="@_alarmTriggerConfig"
                                                         ValueChanged="@(v => _alarmTriggerConfig = v)"
-                                                        AvailableAttributes="@BuildAlarmAttributeChoices()" />
+                                                        AvailableAttributes="@BuildAlarmAttributeChoices()"
+                                                        FallbackPriority="@_alarmPriority" />
                                 </div>
                                 <div class="col-12">
                                     <div class="form-check">