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/Controllers/ClientToServer/DataController.cs

@@ -48,7 +48,7 @@ namespace PrivaPub.Controllers.ClientToServer
 			catch (Exception ex)
 			{
 				Logger.LogError(ex, $"{nameof(DataController)}.{nameof(Languages)}()");
-				return BadRequest(result.Invalidate(ex.Message, exception: ex));
+				return BadRequest(result.Invalidate("Something went wrong.", exception: ex));
 			}
 		}
 	}