feat(ui/templates): structured trigger editor for template scripts

The script add/edit modal exposed a script's trigger as two raw free-text
inputs — a type string and hand-written config JSON — with no validation
and no parity with the alarm trigger UI.

Replace them with a ScriptTriggerEditor component (mirroring
AlarmTriggerEditor): a trigger-type dropdown plus type-specific panels for
Interval, ValueChange, Conditional, and Call, a grouped attribute picker,
and an auto-generated hint. A ScriptTriggerConfigCodec round-trips the
TriggerConfiguration JSON the site runtime's ScriptActor consumes, tolerant
of legacy keys; an unrecognized stored type is preserved untouched in a
read-only panel.

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

@@ -874,13 +874,12 @@
                                     <label class="form-label">Name</label>
                                     <input type="text" class="form-control" @bind="_scriptName" readonly="@editingScript" />
                                 </div>
-                                <div class="col-md-6">
-                                    <label class="form-label">Trigger Type</label>
-                                    <input type="text" class="form-control" @bind="_scriptTriggerType" placeholder="e.g. ValueChange" />
-                                </div>
-                                <div class="col-md-6">
-                                    <label class="form-label">Trigger Config (JSON)</label>
-                                    <input type="text" class="form-control" @bind="_scriptTriggerConfig" />
+                                <div class="col-12">
+                                    <label class="form-label">Trigger</label>
+                                    <ScriptTriggerEditor TriggerType="@_scriptTriggerType"
+                                                         TriggerConfig="@_scriptTriggerConfig"
+                                                         Changed="@OnScriptTriggerChanged"
+                                                         AvailableAttributes="@BuildAlarmAttributeChoices()" />
                                 </div>
                                 <div class="col-12">
                                     <div class="form-check">
@@ -1456,6 +1455,13 @@
         else { _toast.ShowError(result.Error); }
     }
 
+    /// <summary>Applies the structured trigger editor's type + config atomically.</summary>
+    private void OnScriptTriggerChanged(ScriptTriggerValue v)
+    {
+        _scriptTriggerType = v.TriggerType;
+        _scriptTriggerConfig = v.Config;
+    }
+
     private void BeginAddScript()
     {
         _showScriptForm = true;