Point metadata and README at Federated Computer

Federated Computer is the developer, CoreDesktop's site the homepage,
and the federated-calendar repository's issues the bug tracker and
support. Drop the GNOME links and project group, which don't apply
here; the About dialog now takes its support link from the metainfo.

The README says Federated Calendar is based on GNOME Calendar, links
to it, and explains how to build and run it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -1,32 +1,53 @@
 <div align="center">
-  <img src="data/icons/hicolor/scalable/apps/org.gnome.Calendar.svg" width="128" height="128">
+  <img src="data/icons/hicolor/scalable/apps/computer.federated.FederatedCalendar.svg" width="128" height="128">
 
-  # GNOME Calendar
+  # Federated Calendar
 
   Manage your schedule
-
-  <img width="922" src="https://static.gnome.org/appdata/gnome-50/org.gnome.Calendar/month-view.png">
 </div>
 
-## Installation
+Federated Calendar is a calendar app for [CoreDesktop] that works with the
+calendars of your Federated Computer Core. Invite people to your events by
+email, and your Core sends them the invitations, updates and cancellations.
 
-[![Flatpak](https://flathub.org/api/badge?svg&locale=en)](https://flathub.org/apps/details/org.gnome.Calendar)
+It's based on [GNOME Calendar], and can be installed alongside it.
+
+## Inviting people
+
+People can be invited to events on the calendars of a Core that CoreDesktop's
+`configure` has set up on this computer. You become the event's organizer, and
+the Core's Nextcloud emails the invitations when you save the event.
+
+## Building
+
+```sh
+meson setup _build
+ninja -C _build
+```
+
+To run it without installing:
+
+```sh
+GSETTINGS_SCHEMA_DIR=_build/data ./_build/src/federated-calendar
+```
+
+To install it in `/usr/local`:
+
+```sh
+sudo ninja -C _build install
+```
 
 ## Links
 
-- Homepage: [apps.gnome.org/Calendar]
-- Report an issue: [gitlab.gnome.org/GNOME/gnome-calendar/issues]
-- Donate: [donate.gnome.org]
-- Translate: [l10n.gnome.org/module/gnome-calendar]
-- Contact: [matrix.to/#/#gnome-calendar:gnome.org]
+- Homepage: [coredesktop.computer][CoreDesktop]
+- Report an issue: [gitea.federated.computer/Federated_Computer/federated-calendar/issues]
+- Based on: [GNOME Calendar]
 
 ## Contributing
 
 For information on how to contribute, please check [CONTRIBUTING.md](CONTRIBUTING.md) and [HACKING.md](HACKING.md).
 
 
-[apps.gnome.org/Calendar]: https://apps.gnome.org/Calendar
-[gitlab.gnome.org/GNOME/gnome-calendar/issues]: https://gitlab.gnome.org/GNOME/gnome-calendar/issues/
-[donate.gnome.org]: https://donate.gnome.org/
-[l10n.gnome.org/module/gnome-calendar]: https://l10n.gnome.org/module/gnome-calendar/
-[matrix.to/#/#gnome-calendar:gnome.org]: https://matrix.to/#/#gnome-calendar:gnome.org/
+[CoreDesktop]: https://coredesktop.computer
+[GNOME Calendar]: https://gitlab.gnome.org/GNOME/gnome-calendar
+[gitea.federated.computer/Federated_Computer/federated-calendar/issues]: https://gitea.federated.computer/Federated_Computer/federated-calendar/issues