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>

app/src/main/AndroidManifest.xml

@@ -30,7 +30,7 @@
     </queries>
 
     <application
-        android:name=".FloretApp"
+        android:name=".AgendulaApp"
         android:allowBackup="true"
         android:dataExtractionRules="@xml/data_extraction_rules"
         android:fullBackupContent="@xml/backup_rules"
@@ -39,7 +39,7 @@
         android:localeConfig="@xml/locales_config"
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
-        android:theme="@style/Theme.Floret"
+        android:theme="@style/Theme.Agendula"
         tools:targetApi="35">
         <activity
             android:name=".MainActivity"