fix(auth): GitHub-only accounts go at GitHub's end; only the anonymous add an address

The full reading's M1 and L6: once GitHub IDs were forgotten at
GITHUB_SIGN_IN_ENDS, an account that had signed in with GitHub alone
counted as anonymous, so a stolen session and any mailbox gave it a first
password and authenticator; and such accounts, with no way in left, were
never pruned. Now:

- at the end, the daily run that forgets the GitHub IDs first deletes the
  accounts that sign in with GitHub alone (no address, so never a
  password), with everything they have, members told (deletePerson); the
  app tells them for the three months before that their account goes then
  unless they set up a password (passwordSectionGitHubEndsDeletes, en/de);
- password.set adds an address without GitHub only for someone anonymous
  where the session lives (anonymousHere, which a member tells the
  register, as it tells freshGitHubSignIn); anyone else is refused before
  any code is used.

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_app/lib/l10n/halkyon_app_de.arb

@@ -231,5 +231,6 @@
   "passwordResetsAccount": "Am {date} bekommt dein Konto ein neues Passwort und neue Schlüssel, und was mit den alten verschlüsselt ist, geht verloren: Jemand hat es mit einem Code per Mail angefordert. Warst du das nicht, sag es ab.",
   "passwordResetsCallOff": "Absagen",
   "passwordCallOffTitle": "Zurücksetzen absagen",
-  "passwordCallOffIntro": "Dein Passwort und ein Code sagen jedes anstehende Zurücksetzen ab."
+  "passwordCallOffIntro": "Dein Passwort und ein Code sagen jedes anstehende Zurücksetzen ab.",
+  "passwordSectionGitHubEndsDeletes": "Die Anmeldung mit GitHub endet am {date}. Dann wird dein Konto mit allem darin gelöscht, es sei denn, du richtest vorher ein Passwort ein."
 }