feat(app): tag, edit, delete and swipe cards while studying, with tidier session sheets

- Above every studied card (but a matching one): the PDF it came from,
  its tags on one line ("+2 tags" for the rest) or "Add tags", and a
  menu to tag, edit or delete it; the session follows (an edited card
  shows as saved, a deleted one leaves the round).
- On phones, a front/back or vocabulary card swiped right is rated
  Good, left Bad; it tilts over the colour it heads for, and springs
  back when let go early.
- The session's settings: "Settings", a 48 dp Save that warns mid-round
  ("Heads up!"), steppers in an outlined box ("20 / day", "5 / 50"),
  the order in an outlined dropdown, the chosen tags with the rest
  behind "Filter by tags" / "+3 more".
- A studyset's study options: Save above Reset to defaults, the
  description small, reviews a day in steps of 25.
- One stepper look everywhere (study, Pomodoro profiles), its buttons
  "Decrease" and "Increase".

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

halkyon_learn_flutter/lib/l10n/app_localizations_de.dart

@@ -1166,13 +1166,9 @@ class AppLocalizationsDe extends AppLocalizations {
   @override
   String get studySettingsFilterByTags => 'Nach Tags filtern';
 
-  @override
-  String get studySettingsFilterHint =>
-      'Lerne nur die Karteikarten mit mindestens einem der gewählten Tags.';
-
   @override
   String get studySettingsNoTags =>
-      'Noch keine Tags. Füge deinen Karteikarten Tags hinzu, um sie hier zu filtern.';
+      'Noch keine Inhalts-Tags. Füge deinen Karten Tags hinzu, um sie hier zu filtern.';
 
   @override
   String get studySettingsReset => 'Zurücksetzen';
@@ -1180,6 +1176,24 @@ class AppLocalizationsDe extends AppLocalizations {
   @override
   String get studySettingsSave => 'Speichern';
 
+  @override
+  String get studySettingsHeadsUpTitle => 'Achtung!';
+
+  @override
+  String get studySettingsHeadsUpBody =>
+      'Die vorgenommenen Änderungen laden die Sitzung neu und dein aktueller Fortschritt geht verloren.';
+
+  @override
+  String get studySettingsApplyChanges => 'Änderungen übernehmen';
+
+  @override
+  String get studySettingsPerDay => ' / Tag';
+
+  @override
+  String studySettingsMoreTags(int count) {
+    return '+$count weitere';
+  }
+
   @override
   String get cardTagsLabel => 'Tags';
 
@@ -1189,6 +1203,17 @@ class AppLocalizationsDe extends AppLocalizations {
   @override
   String get cardTagsEdit => 'Tags bearbeiten';
 
+  @override
+  String tagChipsOverflow(int count) {
+    String _temp0 = intl.Intl.pluralLogic(
+      count,
+      locale: localeName,
+      other: '$count Tags',
+      one: '1 Tag',
+    );
+    return '+$_temp0';
+  }
+
   @override
   String get cardFilterTooltip => 'Filter';
 
@@ -1803,10 +1828,6 @@ class AppLocalizationsDe extends AppLocalizations {
   @override
   String get studyOptionsReviewsPerDay => 'Wiederholungen pro Tag';
 
-  @override
-  String get studyOptionsReviewsPerDayHint =>
-      'Karten in ihren Lernschritten kommen trotzdem.';
-
   @override
   String get studyOptionsOrder => 'Reihenfolge';
 
@@ -1855,10 +1876,10 @@ class AppLocalizationsDe extends AppLocalizations {
   String get studySortNewestFirst => 'Neueste zuerst';
 
   @override
-  String get studyFewer => 'Weniger';
+  String get studyFewer => 'Verringern';
 
   @override
-  String get studyMore => 'Mehr';
+  String get studyMore => 'Erhöhen';
 
   @override
   String get studysetMenuReset => 'Fortschritt zurücksetzen';