feat(app): the dictionary in the app: look words up, add them as cards

A studyset's dictionary follows from its language, as decided: the
instance's dictionary of its front's language, with meanings in its
back's (else English). Nothing to attach or detach; nothing of it shows
where there is none.

- Add material › From the dictionary: search a word (kanji, kana,
  romaji, meaning) and add it as a flashcard, or add a whole level
  (JLPT N5…N1, common words) at once, asked first above 500 words, its
  progress shown. Words already in the studyset show as such and are
  left out. Each card is a vocabulary card (headword, reading, senses
  with their codes), tagged `jlpt-n5` and with its word class, and
  marked as imported from the dictionary.
- Look up beside a vocabulary card's front fills the card with the word
  chosen, keeping its hints, explanation and tags.
- A card keeps the dictionary entry it was made from (card schema 6:
  `dictionary` {source, id}), to be found again and not added twice.
- The dictionary's credits show at its foot and in About, as its licence
  asks.

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

@@ -1743,6 +1743,114 @@ class AppLocalizationsDe extends AppLocalizations {
   @override
   String get cardSenses => 'Wortbedeutungen';
 
+  @override
+  String get cardDictionaryEntry => 'Wörterbucheintrag';
+
+  @override
+  String get studysetFromDictionary => 'Aus dem Wörterbuch';
+
+  @override
+  String get dictionaryTitle => 'Wörterbuch';
+
+  @override
+  String get dictionarySearchHint =>
+      'Ein Wort in Kanji, Kana oder Romaji, oder eine Bedeutung';
+
+  @override
+  String dictionaryNothingFound(String query) {
+    return 'Nichts gefunden für „$query“.';
+  }
+
+  @override
+  String get dictionaryUnreachable =>
+      'Das Wörterbuch ist gerade nicht erreichbar.';
+
+  @override
+  String get dictionaryRetry => 'Erneut versuchen';
+
+  @override
+  String get dictionaryAdd => 'Hinzufügen';
+
+  @override
+  String get dictionaryInStudyset => 'In diesem Lernset';
+
+  @override
+  String dictionaryAdded(String word) {
+    return '„$word“ hinzugefügt.';
+  }
+
+  @override
+  String get dictionaryLevels => 'Eine ganze Stufe hinzufügen';
+
+  @override
+  String get dictionaryLevelsHint =>
+      'Jedes Wort einer Stufe wird eine Karteikarte, in der Reihenfolge ihrer Liste, mit Stufe und Wortart als Tags. Wörter, die schon in diesem Lernset sind, werden ausgelassen.';
+
+  @override
+  String get dictionaryLabelCommon => 'Häufig';
+
+  @override
+  String dictionaryAddLevel(int count) {
+    String _temp0 = intl.Intl.pluralLogic(
+      count,
+      locale: localeName,
+      other: '$count Wörter hinzufügen',
+      one: '1 Wort hinzufügen',
+    );
+    return '$_temp0';
+  }
+
+  @override
+  String dictionaryAddingLevel(int done, int count) {
+    return 'Wird hinzugefügt… $done von $count';
+  }
+
+  @override
+  String dictionaryWordsAdded(int count) {
+    String _temp0 = intl.Intl.pluralLogic(
+      count,
+      locale: localeName,
+      other: '$count Wörter hinzugefügt.',
+      one: '1 Wort hinzugefügt.',
+      zero: 'Keine neuen Wörter.',
+    );
+    return '$_temp0';
+  }
+
+  @override
+  String dictionaryWordsSkipped(int count) {
+    String _temp0 = intl.Intl.pluralLogic(
+      count,
+      locale: localeName,
+      other: '$count waren schon in diesem Lernset.',
+      one: '1 war schon in diesem Lernset.',
+    );
+    return '$_temp0';
+  }
+
+  @override
+  String dictionaryConfirmTitle(int count) {
+    return '$count Wörter hinzufügen?';
+  }
+
+  @override
+  String get dictionaryConfirmMessage =>
+      'Jedes wird eine Karteikarte in diesem Lernset.';
+
+  @override
+  String get dictionaryConfirmAdd => 'Hinzufügen';
+
+  @override
+  String dictionaryCredits(String sources) {
+    return 'Wörter aus $sources.';
+  }
+
+  @override
+  String get dictionaryLookUp => 'Im Wörterbuch nachschlagen';
+
+  @override
+  String get aboutDictionaries => 'Wörterbücher dieser Instanz';
+
   @override
   String get cardReportTitle => 'Fehler melden';