feat(base)!: removing a profile makes it private (ADR 0020, D27)

Every account keeps a handle now, so removing a public profile no
longer deletes it and frees the handle: it takes away what the profile
shows and leaves it private, as a profile is until its person goes
public (D5).

- `profile.remove` and the register's `removeProfile` (members ask the
  register) empty the display name, bio, links with their checks and
  the avatar, keep the row with its handle, and return what is left,
  null for none. `/@handle` and `profiles.byHandle` then answer as for
  a handle nobody has. Once the person has published, removing is
  refused as before.
- Learn: the profile form starts afresh from what is left, "Remove
  profile" shows only while something is filled in, and the dialog says
  the handle stays.
- The module's README and ADR 0020 amended.

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/README.md

@@ -24,7 +24,7 @@ Endpoints, under the nickname `base` in a host's client (`client.modules.base.em
 | `emailCode` | `sendCode`: a code by mail, which proves the address and signs nobody in | anyone |
 | `account` | `delete` (with the password's proof where the account has one, `keysProof` for one that signs in with SimpleLogin), `signInWays` | signed in |
 | `instance` | `basics`: the app it serves, GitHub's client ID if any and when GitHub sign-in ends, whether codes by mail, password sign-in and SimpleLogin are on, the source link, the oldest app build, where data and backups are | anyone |
-| `profile` | `mine`, `save`, `checkHandle` (with every answer about a new handle, at most 30 an hour per person and 60 per network), `checkLinks` (at most 10 an hour), `setAvatar`, `removeAvatar`, `remove`: the caller's own public profile | `identified` |
+| `profile` | `mine`, `save`, `checkHandle` (with every answer about a new handle, at most 30 an hour per person and 60 per network), `checkLinks` (at most 10 an hour), `setAvatar`, `removeAvatar`, `remove` (what it shows goes, the handle stays, private again: Halkyon Learn's ADR 0020, D27): the caller's own public profile | `identified` |
 | `profiles` | `byHandle`: anyone's public profile once they went public, whatever the handle's case | signed in |
 
 - GitHub keeps only the numeric GitHub ID, in Serverpod's own table; email keeps only