feat(learn): furigana and pinyin over hints, from Tatoeba's transcriptions

The curator puts Tatoeba's readings on a dictionary's examples by their
Tatoeba ID (`withTatoebaReadings`, `curate readings`, and in `update`):
furigana over JMdict's Japanese from its jpn transcriptions, pinyin with
tone marks over Chinese from its cmn ones, each word over as many Han
characters as it has syllables. An example gets `ruby`, `[start, end,
reading]` each, and `rubyUnreviewed` where no one wrote or checked them
(MeCab's furigana, the automatic pinyin). JMdict's conversion goes to 3,
so instances convert again at once.

A word's example hints carry them as ruby marks, the word still in bold.
The hints sheet shows them from the start with a switch above
(Furigana, Pinyin), kept on the device (`DeviceSettings.hintReadings`),
and below a hint whose readings no one reviewed says so.

Whats-New: Example sentences in a word's hints now show furigana or pinyin over them, with a switch to hide them.
Whats-New-De: Beispielsätze in den Hinweisen eines Worts zeigen jetzt Furigana oder Pinyin darüber, mit einem Schalter zum Ausblenden.

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

apps/learn/halkyon_learn_curator/test/fixtures/tatoeba-cmn_transcriptions.tsv

@@ -0,0 +1,8 @@
+750344	cmn	Hant		我學習。
+750344	cmn	Latn		Wo3 xue2xi2.
+332662	cmn	Hant		您學習嗎？
+332662	cmn	Latn	Yorwba	Nin2 xue2xi2 ma5?
+4456365	cmn	Hant		她學習數學
+4456365	cmn	Latn		Ta1 xue2xi2 shu4xue2
+333376	cmn	Hant		我妹妹目前不學習。
+333376	cmn	Latn	Yorwba	Wo3 mei4mei5 mu4qian2 bu4 xue2xi2.

apps/learn/halkyon_learn_curator/test/fixtures/tatoeba-jpn_transcriptions.tsv

@@ -0,0 +1,3 @@
+193344	jpn	Hrkt	Waldelfe	もっと[果物|くだ|もの]を[食|た]べるべきです。
+81964	jpn	Hrkt		[僕|ぼく]は[脚本|きゃく|ほん][家|か]で[食|た]べていく[決心|けっ|しん]をした。
+232489	jpn	Hrkt		あなたはどこでテレビを[見|み]ますか。