fix(dictionary): its sources in a short line, the full credits a tap away

The foot of the dictionary named each source with its makers and
licence, three lines of small print. It now names the sources alone in
a line ("Words from JMdict, JLPT vocabulary lists, Tatoeba"); tapping
it or its ⓘ shows who made each, under which licence, with its link,
which is still where the entries show, as the licences ask.

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_de.arb

@@ -640,6 +640,7 @@
   "dictionaryConfirmMessage": "Jedes wird eine Karteikarte in diesem Lernset.",
   "dictionaryConfirmAdd": "Hinzufügen",
   "dictionaryCredits": "Wörter aus {sources}.",
+  "dictionarySourcesTitle": "Quellen",
   "dictionaryLookUp": "Im Wörterbuch nachschlagen",
   "dictionaryCharacterSearchHint": "Ein Kanji oder Kana, eine Lesung in Kana oder Romaji, oder eine Bedeutung",
   "dictionaryTabWords": "Wörter",