feat(auth)!: codes by mail no longer sign in

ADR 0017, step 3 (D4: nobody signs in with email codes yet, so the
password replaces them outright). `emailCode.verifyCode`,
`emailSignIn.signIn` and the switch token go, with the register's
`verifySignInCode` and `completeEmailSwitch` and their operations
between services. `emailCode.sendCode` stays, now without a session
(signing up and getting back in have none), as what proves an address
for a password's setup, a sign-up, a setup never finished and the
resets; `accountRecovery.sendCode`, which did that for the resets,
goes. The `switchChallengeId` column stays: Serverpod's challenges
still link a completion token, and older servers read it during a
deploy.

The apps: halkyon_app's email sign-in (its bloc, sheet, gateway calls
and the start screen's Continue with email) goes; Learn's profile and
Todo's account sheet show `AccountSecuritySection` (a password set up
by someone anonymous or signing in with GitHub, whose end it names;
the authenticators; changing the password; new recovery codes and
phrase), which reads anew after every change the repository makes.

BREAKING CHANGE: Learn's `minimumAppBuild` is 22: builds up to 21 sign
in with the endpoints that went. Todo was never released and stays at
build 1.

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/lib/src/register/account_register.dart

@@ -119,24 +119,6 @@ abstract interface class AccountRegister {
     required String network,
   });
 
-  /// Accepts [code] for [request] from [person]: the address becomes theirs
-  /// (an account of the register, under their ID) unless it is another
-  /// person's, whose switch token it then gives. Refusals as
-  /// `acceptSignInCode`'s.
-  Future<EmailCodeAccepted> verifySignInCode(
-    Session session, {
-    required UuidValue person,
-    required UuidValue request,
-    required String code,
-  });
-
-  /// The account a switch token names, once only. Refusals as
-  /// `completeEmailSwitch`'s.
-  Future<UuidValue> completeEmailSwitch(
-    Session session, {
-    required String switchToken,
-  });
-
   /// Links the GitHub account [gitHubUserId] to [person] (an account of the
   /// register, under their ID). Refusals as `linkGitHubAccount`'s.
   Future<void> linkGitHub(