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_de.dart

@@ -1558,6 +1558,72 @@ class AppLocalizationsDe extends AppLocalizations {
   @override
   String get profileTitle => 'Profil';
 
+  @override
+  String get profileTabProfile => 'Profil';
+
+  @override
+  String get profileTabStatistics => 'Statistik';
+
+  @override
+  String get statisticsDays => 'Tage';
+
+  @override
+  String get statisticsWeeks => 'Wochen';
+
+  @override
+  String get statisticsMonths => 'Monate';
+
+  @override
+  String get statisticsTotal => 'Insgesamt';
+
+  @override
+  String get statisticsPerDay => 'Pro Tag';
+
+  @override
+  String get statisticsRecord => 'Tagesrekord';
+
+  @override
+  String get statisticsStudyTime => 'Lernzeit';
+
+  @override
+  String get statisticsMinutesInfo =>
+      'In Minuten, jede Karte höchstens eine Minute gezählt';
+
+  @override
+  String get statisticsHoursInfo =>
+      'In Stunden, jede Karte höchstens eine Minute gezählt';
+
+  @override
+  String get statisticsRatings => 'Bewertungen';
+
+  @override
+  String get statisticsRatingsInfo =>
+      'Wie du die gelernten Karteikarten bewertet hast';
+
+  @override
+  String statisticsRated(int count) {
+    String _temp0 = intl.Intl.pluralLogic(
+      count,
+      locale: localeName,
+      other: '$count Karten bewertet',
+      one: '1 Karte bewertet',
+      zero: 'Keine Karte bewertet',
+    );
+    return '$_temp0';
+  }
+
+  @override
+  String get statisticsToday => 'Heute';
+
+  @override
+  String statisticsWeekOf(String date) {
+    return 'Woche ab $date';
+  }
+
+  @override
+  String get statisticsNothingYet =>
+      'Noch nichts gelernt. Deine Lernzeit und Bewertungen erscheinen hier, sobald du Karteikarten lernst.';
+
   @override
   String get profileSettingsTooltip => 'Einstellungen';
 
@@ -6222,7 +6288,7 @@ class AppLocalizationsDe extends AppLocalizations {
 
   @override
   String get progressStudyTimeInfo =>
-      'Wie lange du die Karteikarten dieses Lernsets in den letzten sieben Tagen auf diesem Gerät gelernt hast.';
+      'Wie lange du die Karteikarten dieses Lernsets in den letzten sieben Tagen gelernt hast, jede Karte höchstens eine Minute gezählt.';
 
   @override
   String get progressThisWeek => 'diese Woche';