R2 accounts are safe: email by password and code, recovery only to it, sessions that end

Completion program R2 (docs/ROADMAP.md, 2026-10-17).

- An email address is set only with the password and a 6-digit code sent to it: /clientapi/user/email, /email/verify,
  /email/remove and GET /clientapi/user/account (EmailVerification: an hour, five tries, the code's hash only;
  EmailVerificationJob through the new IMailer). The request answers one sentence whether or not the address is free,
  and nothing goes to an address another login verified. The old POST /clientapi/user/update, which changed the
  address with neither and said when one was taken, answers 422.
- Recovery writes only to a verified address; migration _019 keeps the addresses given before verification existed.
- A changed password ends every session and every persona token, and answers a new JWT for the device that changed it.
- Sessions: every JWT carries its session's id ("si", kept by sniff/again). GET /clientapi/user/logout, which did
  nothing, ends that session alone (RootUser.EndedSessions, until its tokens would expire); POST
  /clientapi/user/logout/everywhere ends them all.
- AppConfiguration:HashingOptions was never bound, so passwords were hashed at the default 9789 iterations: it is
  bound now, at 210,000, and a hash made at other iterations is made again at the next sign-in (matched on the old
  hash, so two sign-ins never undo each other).
- Recovery and verification codes expire through TTL indexes; EmailVerification is never in a backup.
- AppConfigurationService reads appsettings as they are now, not the copy older builds saved in Mongo on first boot.
- ViewUserSettings and RootUserSettings carry SavedAt, so a client signing in keeps its own theme until one saved.
- Pasture: peers/mailpit.sh (Mailpit 1.31.4 as mailpit.test) receives PrivaPub's mail; recovery links open
  https://decepub.test. scenarios/accounts.sh, in sweep batch A, checks all of the above (28 checks).

Verified: dotnet build PrivaPub.sln -c Release; the pasture with gts and mailpit: accounts 28/28 and gts, 91 passed,
0 failed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WpVCoDeM1qUTRp4fXQdfof

PrivaPub/Models/User/RootUser.cs

@@ -21,6 +21,7 @@ namespace PrivaPub.Models.User
 		public DateTime? DeletedAt { get; set; }
 		public DateTime? CredentialsChangedAt { get; set; }//when RootSessions last ended every session
 		public string SessionStamp { get; set; }//carried by every /clientapi token; a new one ends the tokens issued before
+		public List<EndedSession> EndedSessions { get; set; } = new();//sessions signed out one by one, until their tokens expire
 
 		/// <summary>An administrator is a moderator too (IsAdminPolicy asks for both); otherwise a plain user.</summary>
 		public void SetAdmin(bool admin)
@@ -34,9 +35,17 @@ namespace PrivaPub.Models.User
 		}
 	}
 
+	// a session that signed out: its tokens carry Sid, and are refused until Until, when they would have expired anyway
+	public class EndedSession
+	{
+		public string Sid { get; set; }
+		public DateTime Until { get; set; }
+	}
+
 	public class RootUserSettings
 	{
 		public string LanguageCode { get; set; } = "en-GB";
+		public DateTime? SavedAt { get; set; }//when a client last saved them; until then a client keeps its own
 
 		public short IconsThemeIndexColour { get; set; } = 25;
 		public short LightThemeIndexColour { get; set; } = 25;