fix(reminders): show the day for reminders on another day (#46)

A reminder fired ahead of an event on a different day showed only the
event's time (e.g. "09:30 – 10:00"), making it look like it was
happening today. reminderTimeText now prefixes timed events with a
relative day: "Tomorrow"/"Yesterday", the short weekday for another day
this week, or the exact date for anything further out.

The this-week boundary honours the user's "week starts on" setting: the
resolved first day of week is threaded through from ReminderNotifier, so
e.g. a Sunday reads as next week under a Sunday-start locale. All-day
events keep their explicit date (never ambiguous), and cross-midnight
timed events keep both explicit dates.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/src/main/res/values/strings.xml

@@ -226,6 +226,9 @@
     <string name="reminder_onboarding_skip_button">Not now</string>
     <string name="reminder_action_snooze">Snooze</string>
     <string name="reminder_action_dismiss">Dismiss</string>
+    <!-- Day context prefix in a reminder for an event on another day (v2.15.0) -->
+    <string name="reminder_day_tomorrow">Tomorrow</string>
+    <string name="reminder_day_yesterday">Yesterday</string>
 
     <!-- View switcher (M1) -->
     <string name="view_month">Month</string>