fix(auth)!: a session alone never gets a code checked

The third reading found a stolen session guessing TOTP codes without end:
nine wrong codes for new recovery codes, then removing an unconfirmed
authenticator of its own, a success that cleared the session's count. As
Proton has it, every signed-in change of how an account is secured now
takes the owner's proof (OwnerProof): the password's SRP proof for a
change's challenge and a TOTP or recovery code. Adding an authenticator
once one is confirmed, removing a confirmed one, new recovery codes, a new
phrase, a new password and deleting take it; only the first authenticator
is confirmed with its own code alone, and removing an unconfirmed one
takes nothing. A proof given where none is taken is refused, and a
confirmed authenticator's code is never checked for a session alone, so
no success passes a proof unchecked.

A session's proofs count for it alone, before they are checked, cleared
only by one accepted; the tenth wrong in a row ends the session. They
never count toward the account's waits nor wait for them, so whoever
knows the password no longer holds a signed-in owner out of changing it
(the second finding), and a new password forgets those waits. Beginning a
change counts nothing against the account (the third finding): 30 an
hour per session, holding back that session alone. Deleting takes a TOTP
code wherever an authenticator is confirmed, a code by mail where no
second factor works (the fourth finding), which SignInWays now tells
(secondFactorWorks). Signed-in calls no longer take the address: nothing
there mails. wrongExistingCode goes, a wrong existing code being a wrong
proof.

The app follows in the next commit.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

packages/halkyon_base_server/test/integration/support/password_device.dart

@@ -155,6 +155,27 @@ final class PasswordDevice {
     );
   }
 
+  /// The owner's proof for [challenge] (a change's): the device's answer
+  /// with its password, or the [privateValue] of another, and a
+  /// [totpCode] or [recoveryCode].
+  OwnerProof ownerProof(
+    PasswordChallenge challenge, {
+    String? totpCode,
+    String? recoveryCode,
+    BigInt? privateValue,
+    String host = testHost,
+  }) {
+    final reply = answer(challenge, privateValue: privateValue, host: host);
+    return OwnerProof(
+      challenge: challenge.challenge,
+      clientValue: reply.clientValue,
+      clientProof: reply.clientProof,
+      host: host,
+      totpCode: totpCode,
+      recoveryCode: recoveryCode,
+    );
+  }
+
   /// The signature proving the recovery phrase for [challenge] on [host]:
   /// for the new [password] it sets, or for an authenticator's reset
   /// without one; by the phrase's proof key, or [keys]' where given.