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>

packages/halkyon_base_server/README.md

@@ -484,7 +484,7 @@ Built on the three parts above, on the register (members forward every step thro
      HalkyonBase(
        app: 'todo', // its apps accept only instances naming it; never change it
        appName: 'Halkyon Todo', // in sign-in mails
-       upstreamSourceCodeUrl: 'https://code.halkyon.app/project-halkyon/halkyon_todo',
+       upstreamSourceCodeUrl: 'https://code.halkyon.app/halkyon-days/halkyon',
        minimumAppBuild: 1, // raise it in the commit that breaks older apps
        deletePersonData: [deleteTodosOf], // the host's own data of a person
        profilePageNote: ( // what profile pages say of the app at their foot