feat(uns): validate typed TagConfig before save (F-uns-2 / #156)

The per-driver editor models expose Validate() (required-field checks) but the
TagModal never called them, so a blank required field (e.g. S7 address, AbCip
tag path) saved silently and only failed at deploy/connect. Add a
TagConfigValidator registry (DriverType -> model.FromJson(json).Validate(),
parallel to TagConfigEditorMap) and call it in SaveAsync before the service
call — a non-null result sets the modal error and blocks save. Unmapped drivers
(no typed editor) and Modbus (no required field) return null. Editors untouched.

AdminUI.Tests 307/307 (12 new validator tests); build clean.

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Uns/TagModal.razor

@@ -197,6 +197,15 @@
         _error = null;
         try
         {
+            // Client-side per-driver config validation (the typed editor's Validate()), so a blank
+            // required field is caught here rather than silently saving and failing at deploy/connect.
+            var configError = TagConfigValidator.Validate(SelectedDriverType, _form.TagConfig);
+            if (configError is not null)
+            {
+                _error = configError;
+                return;
+            }
+
             var input = new TagInput(
                 _form.TagId,
                 _form.Name,

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Uns/TagEditors/TagConfigValidator.cs

@@ -0,0 +1,29 @@
+namespace ZB.MOM.WW.OtOpcUa.AdminUI.Uns.TagEditors;
+
+/// <summary>
+/// Client-side TagConfig validation dispatched by <c>DriverType</c> (parallel to
+/// <see cref="TagConfigEditorMap"/>). Each entry parses the tag's config JSON into the driver's typed
+/// model and runs its <c>Validate()</c>. Returns an error string to block the TagModal save, or null
+/// when the config is valid — or when no typed validator is registered (unmapped drivers use the raw
+/// textarea and are validated server-side at deploy).
+/// </summary>
+public static class TagConfigValidator
+{
+    private static readonly IReadOnlyDictionary<string, Func<string?, string?>> Validators =
+        new Dictionary<string, Func<string?, string?>>(StringComparer.OrdinalIgnoreCase)
+        {
+            ["ModbusTcp"] = j => ModbusTagConfigModel.FromJson(j).Validate(),
+            ["S7"]        = j => S7TagConfigModel.FromJson(j).Validate(),
+            ["AbCip"]     = j => AbCipTagConfigModel.FromJson(j).Validate(),
+            ["AbLegacy"]  = j => AbLegacyTagConfigModel.FromJson(j).Validate(),
+            ["TwinCat"]   = j => TwinCATTagConfigModel.FromJson(j).Validate(),
+            ["Focas"]     = j => FocasTagConfigModel.FromJson(j).Validate(),
+        };
+
+    /// <summary>
+    /// Validates a tag's <paramref name="configJson"/> for the given <paramref name="driverType"/>.
+    /// Returns an error string to block save, or null when valid / no typed validator is registered.
+    /// </summary>
+    public static string? Validate(string? driverType, string? configJson)
+        => driverType is not null && Validators.TryGetValue(driverType, out var v) ? v(configJson) : null;
+}