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>

apps/learn/halkyon_learn_server/lib/src/instance/app_compatibility.dart

@@ -12,4 +12,9 @@
 /// halkyon_base (ADR 0014, decided 2026-10-19): builds up to 20 (v0.17.0) call
 /// endpoints that are gone and can't read the module's refusals, so the server
 /// with the module deploys only together with a release of build 21.
-const minimumAppBuild = 21;
+///
+/// 22 since codes by mail stopped signing in (ADR 0017, decided 2026-10-20):
+/// builds up to 21 sign in with `emailCode.verifyCode` and
+/// `emailSignIn.signIn`, which are gone; 22 signs in with a password and
+/// TOTP.
+const minimumAppBuild = 22;