Rename app Floret → Agendula

Floret is promoted to the family / design-language (shared-kit) name; the
tasks app itself becomes Agendula (de.jeanlucmakiola.agendula) — agenda
('things to be done') + Calendula's -ula, a twin of the Calendula name.

Renames the package, namespace, applicationId, rootProject.name, app_name,
FloretApp/FloretNavHost/FloretTransitions classes, theme, F-Droid metadata
dir, CI artifact name, and docs. The botanical word 'florets' is preserved in
the name-origin prose, which is rewritten to Agendula's etymology. Clean
build + unit tests green.

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

CHANGELOG.md

@@ -8,7 +8,7 @@ the source of truth for version codes (see Calendula's `docs/RELEASING.md`).
 
 ### Added
 - M5 reminders onboarding & polish: a one-time reminder onboarding step after the
-  provider grant explains that Floret delivers due reminders itself and requests
+  provider grant explains that Agendula delivers due reminders itself and requests
   `POST_NOTIFICATIONS` (API 33+). A new **Settings** screen (gear on the lists
   overview), structured after Calendula as a category hub with sliding sub-screens
   (`CollapsingScaffold` + grouped category rows + full-screen `OptionPicker`):