No admin by username, no Swagger in production, no exception text to clients

S14 and the privacy items of P0:
- signing up as "admin" no longer grants admin; `PrivaPub admin promote
  <root>` (and `demote`) does, run on the box against the configured
  database;
- Swagger is served in Development only;
- every service and controller answers "Something went wrong." where it
  used to send ex.Message, and the SMTP warnings no longer log the
  recipient's address;
- sign-up and login no longer log the IP, User-Agent and root id together;
- invitation sign-up takes the persona's own AvatarUserName (and optional
  AvatarName) instead of naming the avatar after the private login, and
  refuses a persona username equal to the login's. Invitation login uses
  the named persona, creating it if it is new;
- recovery mail comes from "PrivaPub", not collAnon's support address name.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB

PrivaPub.ClientModels/InvitationLoginForm.cs

@@ -10,5 +10,12 @@ namespace PrivaPub.ClientModels
 			StringLength(Constants.GroupInvitationLength, MinimumLength = Constants.GroupInvitationLength,
 				ErrorMessageResourceName = "StringLengthMinMax", ErrorMessageResourceType = typeof(ErrorsResource))]
 		public string InvitationCode { get; set; }
+
+		[StringLength(32, MinimumLength = 3, ErrorMessageResourceName = "StringLengthMinMax", ErrorMessageResourceType = typeof(ErrorsResource)),
+			RegularExpression("^[a-z0-9_]+$", ErrorMessageResourceName = "EmptySpacesNotAllowed", ErrorMessageResourceType = typeof(ErrorsResource))]
+		public string AvatarUserName { get; set; }
+
+		[StringLength(64, ErrorMessageResourceName = "MaxLengthString", ErrorMessageResourceType = typeof(ErrorsResource))]
+		public string AvatarName { get; set; }
 	}
 }