fix(bedtime): name nights by their evening, retry a refused removal

A bedtime before noon now belongs to the evening before, so Sunday to
Thursday nights at 00:30 run early Monday to early Friday, not Saturday
night through Wednesday night. Turning bedtime off clears the "last
applied" state only once the rule is really gone, so a refused removal
is retried instead of leaving Do Not Disturb on. Reopening the screen
after granting access elsewhere creates the rule even if the system's
broadcast never arrived. The empty-mask rule lives in one place.

Refs #1

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

@@ -455,7 +455,7 @@
     <string name="bedtime_section_schedule">Schedule</string>
     <string name="bedtime_start">Bedtime</string>
     <string name="bedtime_wake">Wake up</string>
-    <string name="bedtime_days_hint">The nights bedtime starts on. A wake-up time before the bedtime is the next morning.</string>
+    <string name="bedtime_days_hint">The nights bedtime is for, named by their evening: a bedtime after midnight on Thursday night falls early on Friday. A wake-up time before the bedtime is the next morning.</string>
     <string name="bedtime_section_reminder">Reminder</string>
     <string name="bedtime_reminder">Remind me before bedtime</string>
     <string name="bedtime_reminder_off">Off</string>