feat(profile): statistics beside the profile, a review counting a minute at most

The Profile tab has two tabs, Profile and Statistics, the latter for
anonymous people too: the time studied in all, per day and the most in
one day, and by days, weeks or months the study time and the ratings as
bars, a tap on a bar saying what it holds. The app draws the charts
itself, as the Progress part's sparkline, rather than taking a chart
package.

A review's time was however long its card was shown: one left on the
screen over lunch counted as an hour of study. It now counts at most a
minute, as Anki does by default, here and in a studyset's Progress; the
stored durations stay as they were.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MMm7usAo6q9ZZRoPkWjoxi
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

halkyon_learn_flutter/lib/l10n/app_localizations_en.dart

@@ -1545,6 +1545,72 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get profileTitle => 'Profile';
 
+  @override
+  String get profileTabProfile => 'Profile';
+
+  @override
+  String get profileTabStatistics => 'Statistics';
+
+  @override
+  String get statisticsDays => 'Days';
+
+  @override
+  String get statisticsWeeks => 'Weeks';
+
+  @override
+  String get statisticsMonths => 'Months';
+
+  @override
+  String get statisticsTotal => 'In total';
+
+  @override
+  String get statisticsPerDay => 'Per day';
+
+  @override
+  String get statisticsRecord => 'Daily record';
+
+  @override
+  String get statisticsStudyTime => 'Study time';
+
+  @override
+  String get statisticsMinutesInfo =>
+      'In minutes, each card counted for at most a minute';
+
+  @override
+  String get statisticsHoursInfo =>
+      'In hours, each card counted for at most a minute';
+
+  @override
+  String get statisticsRatings => 'Ratings';
+
+  @override
+  String get statisticsRatingsInfo =>
+      'How you rated the flashcards you studied';
+
+  @override
+  String statisticsRated(int count) {
+    String _temp0 = intl.Intl.pluralLogic(
+      count,
+      locale: localeName,
+      other: '$count cards rated',
+      one: '1 card rated',
+      zero: 'No cards rated',
+    );
+    return '$_temp0';
+  }
+
+  @override
+  String get statisticsToday => 'Today';
+
+  @override
+  String statisticsWeekOf(String date) {
+    return 'Week of $date';
+  }
+
+  @override
+  String get statisticsNothingYet =>
+      'Nothing studied yet. Your study time and ratings show here once you study flashcards.';
+
   @override
   String get profileSettingsTooltip => 'Settings';
 
@@ -6166,7 +6232,7 @@ class AppLocalizationsEn extends AppLocalizations {
 
   @override
   String get progressStudyTimeInfo =>
-      'How long you studied this studyset\'s flashcards on this device in the last seven days.';
+      'How long you studied this studyset\'s flashcards in the last seven days, each card counted for at most a minute.';
 
   @override
   String get progressThisWeek => 'this week';