build: the organisation on code.halkyon.app is halkyon-days

ADR 0045, D12, step 1: project-halkyon was renamed halkyon-days, its
repositories keeping their names. Every URL naming it moves along: the
servers' source-code links, which the AGPL requires, and their tests;
the forks in the pubspecs and the lock (appflowy-editor, pure-zstd,
serverpod-offline-sync); the snaps, the F-Droid listings and the
release configurations; the docs. The curator's credit for the
alphabets names the repository by its name since ADR 0015, halkyon,
rather than halkyon_learn. Forgejo redirects the old addresses until
the name is taken again.

ADRs 0015 and 0039 keep the name they were written with, and the local
folders theirs.

halkyon_editor's gen-l10n caches under build/, committed before its
.gitignore named the folder, are no longer tracked.

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/README.md

@@ -74,7 +74,7 @@ instance's basics; a Serverpod module), `halkyon_app` (instances, sign-in, sync)
   `python3-cairo`); for releases what [Releases](#releases) lists.
 
 The rich-text editor comes from our fork of AppFlowy Editor
-([project-halkyon/appflowy-editor](https://code.halkyon.app/project-halkyon/appflowy-editor)),
+([halkyon-days/appflowy-editor](https://code.halkyon.app/halkyon-days/appflowy-editor)),
 which `flutter pub get` fetches by itself.
 
 ## Running it locally
@@ -128,7 +128,7 @@ the CI runner described in `deploy/runner/`, deploys only commits signed by a ke
 
 ## Releases
 
-Releases are published on [code.halkyon.app](https://code.halkyon.app/project-halkyon/halkyon/releases),
+Releases are published on [code.halkyon.app](https://code.halkyon.app/halkyon-days/halkyon/releases),
 with the APK and the snap, and the APK also in the project's F-Droid repository
 (`https://halkyon.app/fdroid/repo?fingerprint=E8082788756F6B7E682AA22FCEAD24B53E2A8B0912AD66D65E8C2D4F07BB94B0`,
 added in the F-Droid app as a repository). The Snap Store (`halkyon-learn`) follows.