chore(release): prepare v2.8.0

Bump versionName to 2.8.0 (versionCode 20800) — the merge of this to main
is what cuts the release. Move the accumulated 2.8.0 work out of
[Unreleased] into a dated CHANGELOG section and regenerate the F-Droid
per-version changelog.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

fastlane/metadata/android/en-US/changelogs/20800.txt

@@ -0,0 +1,38 @@
+### Added
+- Find events fast. A search button in the top bar of every calendar view opens
+  a search box — type a couple of letters and matching events (by title,
+  location or description) appear, soonest first with past events below. Tap a
+  result to open it. Search covers your whole calendar, not just what's on
+  screen, and skips calendars you've hidden. A recurring event shows its next
+  occurrence rather than the date the series first started.
+- A current-time line in the day and week views. A thin coloured line marks the
+  present moment across today's column, so you can see at a glance where you are
+  in the day. It updates every minute and only appears when today is in view.
+- Add and remove event guests. The create/edit form now has a Guests section:
+  add people by email or pick them from your contacts, mark each as required or
+  optional, and remove them. Calendula never sends invitations itself (it has no
+  internet access) — it only records the guests; if the event lives on a synced
+  account, that account may email them when it syncs, and on a local calendar no
+  one is notified. The form tells you which applies. Picking a guest from
+  contacts needs no contacts permission.
+- Pick a location from your contacts. A contacts button beside the location
+  field drops a contact's address straight into an event — handy for a meeting
+  at someone's home or office. Like the guest picker, it needs no contacts
+  permission.
+- A "New event" Quick Settings tile. Add it to your quick settings to jump
+  straight into the new-event form from anywhere. Settings → New event has a
+  one-tap button to add the tile (Android 13+); on older versions you can add it
+  from the quick-settings editor.
+- Snooze and dismiss buttons on reminder notifications. Dismiss clears the
+  reminder; snooze hides it and brings it back after a delay you pick in
+  Settings → Notifications (5 to 60 minutes, default 10). Android's calendar
+  system won't re-post a reminder on its own, so Calendula schedules an exact
+  alarm to bring a snoozed one back on time.
+
+### Changed
+- Event details now show each guest's email beneath their name, instead of only
+  when no name is available.
+- Crash and problem reports now open on the project's public Codeberg tracker,
+  where anyone can register and file an issue. Nothing is sent automatically —
+  you still review the report and submit it yourself in the browser.
+