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.Host/Components/App.razor

@@ -26,17 +26,54 @@
         </div>
     </div>
 
-    <script src="/_framework/blazor.web.js"></script>
+    <script src="/_framework/blazor.web.js"
+            autostart="false"></script>
     <script>
-        // Reconnection overlay for failover behavior
-        // Blazor object is available after blazor.web.js initializes
+        // Reconnection overlay for failover behavior. After a docker redeploy
+        // (or other server-side restart), Blazor exhausts its retry budget and
+        // leaves the user staring at a stuck "Reconnect failed" overlay. Auto-
+        // reload in that case so the user lands on a fresh circuit instead of
+        // having to manually refresh.
+        Blazor.start({
+            circuit: {
+                reconnectionOptions: {
+                    maxRetries: 8,
+                    retryIntervalMilliseconds: 1500
+                },
+                reconnectionHandler: {
+                    onConnectionDown: () => { /* default overlay */ },
+                    onConnectionUp: () => {
+                        var m = document.getElementById('reconnect-modal');
+                        if (m) m.style.display = 'none';
+                    }
+                }
+            }
+        });
+
         document.addEventListener('DOMContentLoaded', () => {
             if (typeof Blazor !== 'undefined') {
-                Blazor.addEventListener('enhancedload', () => {
-                    document.getElementById('reconnect-modal').style.display = 'none';
+                Blazor.addEventListener?.('enhancedload', () => {
+                    var m = document.getElementById('reconnect-modal');
+                    if (m) m.style.display = 'none';
                 });
             }
         });
+
+        // When Blazor gives up reconnecting, it adds the
+        // `components-reconnect-failed` class to the reconnect modal element.
+        // Watch for it and auto-reload so the user gets a fresh circuit.
+        var mo = new MutationObserver(() => {
+            var m = document.getElementById('reconnect-modal');
+            if (!m) return;
+            if (m.classList.contains('components-reconnect-failed')) {
+                window.location.reload();
+            }
+        });
+        mo.observe(document.documentElement, {
+            attributes: true,
+            subtree: true,
+            attributeFilter: ['class']
+        });
     </script>
     <script src="/js/treeview-storage.js"></script>
     <script src="_content/ScadaLink.CentralUI/js/monaco-init.js"></script>