feat(settings): optional "Calendar" launcher name (#44)

Add a Settings → Appearance toggle that switches the app's launcher label
between "Calendula" and "Calendar", for users on launchers that can't rename
apps themselves.

The launcher entry moves off MainActivity onto two <activity-alias> components
(DefaultNameAlias / CalendarNameAlias); exactly one is enabled at a time via
PackageManager.setComponentEnabledSetting. MainActivity keeps every other intent
filter; the android.app.shortcuts meta-data moves onto both aliases so the
long-press shortcut still publishes. Component-enabled state is the single source
of truth — no persisted preference.

The ComponentName uses the applicationId for the package (carrying the
.debug/.releasetest suffix) and the namespace for the class, since manifest
".Alias" names resolve against the namespace; switching to Calendar enables the
target alias before disabling the other to avoid a zero-entry launcher transient.

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

fastlane/metadata/android/en-US/changelogs/21600.txt

@@ -11,6 +11,11 @@
   setting (Settings → Appearance, off by default) swaps the floating corner
   button for a permanent today icon in the top bar — always there, matching the
   familiar calendar-app pattern. Leave it off to keep the floating button ([#60]).
+- Show the app as "Calendar" in your launcher. A new App name setting
+  (Settings → Appearance) switches the launcher label from "Calendula" to the
+  generic "Calendar" for anyone who prefers it — handy on launchers that can't
+  rename apps themselves. Only the launcher name changes; your home-screen icon
+  may move to a new spot after switching ([#44]).
 
 ### Changed
 - Dates in the Month, Week and Day title bars now follow your language and