feat(sms): make FromNumber optional — support Twilio Messaging-Service-only configs (UI-Med-2)

Code-review finding UI-Med-2: the design doc + delivery adapter treat FromNumber and
MessagingServiceSid as either-or, but the entity ctor, EF schema, UI and CLI all hard-
required FromNumber — so a Messaging-Service-only Twilio config (a normal production
setup) could not be created. Bring the implementation into line with the spec:

- Commons: SmsConfiguration.FromNumber -> string? (ctor fromNumber optional);
  UpdateSmsConfigCommand.FromNumber -> string?.
- ConfigurationDatabase: FromNumber.IsRequired(false) + migration SmsFromNumberOptional
  (ALTER COLUMN nullable, idempotent; Down backfills '' — harmless, MsgSid keeps it
  deliverable) + regenerated model snapshot.
- Transport: SmsConfigDto.FromNumber -> string? (round-trips a Messaging-Service-only config).
- CentralUI: form validation requires AccountSid + at-least-one-of(FromNumber, MsgSid);
  nullable create/edit paths; From-number help text.
- CLI: --from-number no longer Required; BuildUpdateSmsConfigCommand validates the either-or.
- Adapter: From branch null-forgiving (guarded by the existing incomplete-config check).

Tests: ManagementActor MsgSid-only persists null FromNumber; CLI MsgSid-only builds +
neither-throws + contract (--from-number not Required); CentralUI MsgSid-only save.

src/ZB.MOM.WW.ScadaBridge.CLI/Commands/NotificationCommands.cs

@@ -238,8 +238,11 @@ public static class NotificationCommands
         new("--id") { Description = "SMS config ID", Required = true };
     private static readonly Option<string> SmsAccountSidOption =
         new("--account-sid") { Description = "Twilio Account SID", Required = true };
-    private static readonly Option<string> SmsFromNumberOption =
-        new("--from-number") { Description = "Sender phone number (E.164)", Required = true };
+    private static readonly Option<string?> SmsFromNumberOption =
+        new("--from-number")
+        {
+            Description = "Sender phone number (E.164). Provide this and/or --messaging-service-sid.",
+        };
     private static readonly Option<string?> SmsMessagingServiceSidOption =
         new("--messaging-service-sid")
         {
@@ -269,10 +272,18 @@ public static class NotificationCommands
     {
         var id = result.GetValue(SmsIdOption);
         var accountSid = result.GetValue(SmsAccountSidOption)!;
-        var fromNumber = result.GetValue(SmsFromNumberOption)!;
+        var fromNumber = result.GetValue(SmsFromNumberOption);
         var messagingServiceSid = result.GetValue(SmsMessagingServiceSidOption);
         var apiBaseUrl = result.GetValue(SmsApiBaseUrlOption);
         var authToken = result.GetValue(SmsAuthTokenOption);
+        // Whole-replace update: the sender identity must be re-supplied. A Twilio config
+        // needs a From number and/or a Messaging Service SID, so reject the case where the
+        // update would leave neither (mirrors the UI + delivery-adapter validation).
+        if (string.IsNullOrWhiteSpace(fromNumber) && string.IsNullOrWhiteSpace(messagingServiceSid))
+        {
+            throw new ArgumentException(
+                "Provide --from-number and/or --messaging-service-sid (at least one sender identity is required).");
+        }
         return new UpdateSmsConfigCommand(id, accountSid, fromNumber, messagingServiceSid, apiBaseUrl, authToken);
     }