feat(app): the studyset screen laid out as before

The Study pill reads "Learn 12 flashcards" in the app bar and "Learn 12"
floating, "Study" with nothing due, and is off with nothing to study,
saying so. With a path not finished, a chevron beside it offers to start
or continue the path: a menu in the app bar, a Study mode sheet on
phones. The floating bar rises above the licence line, which takes two
lines at most.

Add material offers a path, flashcards, a note and a PDF, in that order;
imports moved to the options' Import content, which asks for a learning
path or an Anki deck. The options read Edit, Move, Study options, Import
content, Reset progress, Archive, Delete. The bibliography is an outlined
round button above the content, and on phones at the foot of the topics.

The tabs sit on a line of their own across the card, what the tab shown
offers beside them: the flashcards' filter and options, and on the paths
Reorder once there are two, which turns them into handles to drag. An
empty tab says so in its middle; tapping the open tab again returns to
its top, and pulling a tab down syncs. The breadcrumb's steps are plain
links between "›", the studyset itself bold. A long description is cut at
a fixed height, measured, with Read more opening it whole under the
studyset's title. A studyset that no longer exists leads back to the
library.

The topics: All topics on the primary colour, in view also while they
are rearranged; each topic with the study it invites in a round icon,
what it holds ("Empty" with nothing, files counted too), and its options
(now with Reset progress) behind "…" or a long press where the finger
is; New sub-studyset at the foot below a line, the list with its
scrollbar always shown. All topics opens Add material while nothing is
due.

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

@@ -191,6 +191,9 @@ class AppLocalizationsDe extends AppLocalizations {
   @override
   String get studysetNoContent => 'Noch kein Inhalt';
 
+  @override
+  String get studysetEmpty => 'Leer';
+
   @override
   String get studysetActionReview => 'Wiederholen';
 
@@ -827,6 +830,72 @@ class AppLocalizationsDe extends AppLocalizations {
     return '$count lernen';
   }
 
+  @override
+  String studysetLearnFlashcards(int count) {
+    String _temp0 = intl.Intl.pluralLogic(
+      count,
+      locale: localeName,
+      other: '$count Karteikarten lernen',
+      one: '1 Karteikarte lernen',
+    );
+    return '$_temp0';
+  }
+
+  @override
+  String get studysetNothingToStudy => 'Noch nichts zu lernen';
+
+  @override
+  String get studysetStudyMode => 'Lernmodus';
+
+  @override
+  String studysetStartPath(String title) {
+    return 'Starten: $title';
+  }
+
+  @override
+  String studysetContinuePath(String title) {
+    return 'Fortsetzen: $title';
+  }
+
+  @override
+  String get studysetStartPathHint =>
+      'Beginne mit dem ersten Schritt dieses Pfads.';
+
+  @override
+  String get studysetContinuePathHint =>
+      'Mach beim nächsten Pfadschritt weiter, wo du aufgehört hast.';
+
+  @override
+  String get studysetSpacedRepetition => 'Verteilte Wiederholung';
+
+  @override
+  String get studysetSpacedRepetitionHint =>
+      'Wiederhole die fälligen Karten, geplant durch FSRS.';
+
+  @override
+  String get studysetImportContent => 'Inhalt importieren';
+
+  @override
+  String get studysetImportPath => 'Lernpfad';
+
+  @override
+  String get studysetImportPathHint => 'Aus einer Halkyon-Pfad-JSON-Datei';
+
+  @override
+  String get studysetImportAnki => 'Anki-Deck';
+
+  @override
+  String get studysetImportAnkiHint => 'Aus einer .apkg- oder .colpkg-Datei';
+
+  @override
+  String get studysetReorder => 'Umsortieren';
+
+  @override
+  String get studysetReorderPaths => 'Pfade umsortieren';
+
+  @override
+  String get studysetReorderDone => 'Fertig';
+
   @override
   String get studysetOpenTopics => 'Themen anzeigen';
 
@@ -846,12 +915,6 @@ class AppLocalizationsDe extends AppLocalizations {
   String get studysetSubStudysetsEmptyHint =>
       'Teile dieses Lernset in Meilensteine oder Lektionen auf.';
 
-  @override
-  String get studysetReorder => 'Umsortieren';
-
-  @override
-  String get studysetReorderDone => 'Fertig';
-
   @override
   String get studysetDragToReorder => 'Zum Umsortieren ziehen';
 
@@ -2430,6 +2493,9 @@ class AppLocalizationsDe extends AppLocalizations {
   String get notFoundGone =>
       'Das gibt es nicht mehr. Vielleicht wurde es auf einem anderen Gerät gelöscht.';
 
+  @override
+  String get studysetBackToLibrary => 'Zurück zur Bibliothek';
+
   @override
   String get fileImage => 'Bild';