feat(ui): structured editors for script schemas and alarm triggers

Replace raw-JSON text inputs with rich UI: script parameter/return types use
a JSON Schema builder (SchemaBuilder + JsonSchemaShapeParser, with a migration
to convert existing definitions); alarm trigger config uses a type-aware
editor with a flattened attribute picker (AlarmTriggerEditor). AlarmActor
gains optional direction (rising/falling/either) on RateOfChange triggers.

src/ScadaLink.CentralUI/Components/Shared/DialogHost.razor

@@ -29,7 +29,8 @@
                     else
                     {
                         <label class="form-label">@state.Body</label>
-                        <input class="form-control form-control-sm"
+                        <input @ref="_promptInputRef"
+                               class="form-control form-control-sm"
                                placeholder="@state.Placeholder"
                                value="@_promptValue"
                                @oninput="OnPromptInput" />
@@ -50,8 +51,10 @@
 
 @code {
     private ElementReference _modalRef;
+    private ElementReference _promptInputRef;
     private string _promptValue = string.Empty;
     private DialogState? _lastSeenState;
+    private DialogState? _focusedForState;
 
     protected override void OnInitialized()
     {
@@ -85,11 +88,26 @@
         {
             try { await JS.InvokeVoidAsync("document.body.classList.add", "modal-open"); }
             catch { /* prerender: no JS — ignore */ }
-            try { await _modalRef.FocusAsync(); }
-            catch { /* element not yet attached: ignore */ }
+
+            // Focus once per opened dialog. Without this guard, every input
+            // keystroke triggers a re-render which would re-focus the modal
+            // element and yank the caret off the prompt input.
+            if (!ReferenceEquals(current, _focusedForState))
+            {
+                _focusedForState = current;
+                try
+                {
+                    if (current.Kind == DialogKind.Prompt)
+                        await _promptInputRef.FocusAsync();
+                    else
+                        await _modalRef.FocusAsync();
+                }
+                catch { /* element not yet attached: ignore */ }
+            }
         }
         else
         {
+            _focusedForState = null;
             try { await JS.InvokeVoidAsync("document.body.classList.remove", "modal-open"); }
             catch { /* prerender: no JS — ignore */ }
         }