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/Pages/Design/ApiMethodForm.razor

@@ -30,11 +30,15 @@
                 </div>
                 <div class="mb-3">
                     <label class="form-label">Parameters</label>
-                    <ParameterListEditor Json="@_params" JsonChanged="@(v => _params = v)" />
+                    <SchemaBuilder Mode="object"
+                                   Value="@_params"
+                                   ValueChanged="@(v => _params = v)" />
                 </div>
                 <div class="mb-3">
                     <label class="form-label">Return value</label>
-                    <ReturnTypeEditor Json="@_returns" JsonChanged="@(v => _returns = v)" />
+                    <SchemaBuilder Mode="value"
+                                   Value="@_returns"
+                                   ValueChanged="@(v => _returns = v)" />
                 </div>
                 <div class="mb-3">
                     <label class="form-label">Script</label>