Replaces the English mirror with native-language equivalents of the
ja string ("この記事には選択した言語の翻訳がありません。元の言語版を表示しています。")
for zh-CN, zh-TW, ko, hi, vi, tr, de, fr, es, pt-BR, ru, uk, it, pl.
Matches the no-:locale-placeholder style already used in ja so the
banner reads naturally in each UI language. en still uses the
parameterized ":locale" version since it's the master template.
The editor's delete-translation button used `__('messages.documents.delete_translation') ?? __('messages.documents.delete')`, but `__()` returns the key string (not null) on miss so the `??` fallback never fires — the button rendered the literal key. Adds the missing key to all 16 locales (en+ja human-translated, others mirror en) and simplifies the blade to a single `__()` call.
Plan doc also reflects the SQLite dropIndex requirement found during Task 2.
DocumentViewer computes viewLocale and isFallback at mount; banner
links authenticated owners to the editor for the current UI locale.
Adds documents.fallback_notice + locale_names to all 16 lang files
(en+ja human-translated, others mirror en for now).
Yutaka Kurosaki
y963admin