i18n(chat): translate the Chat UI strings into all 8 languages

Add the 15 HushChat UI strings (nav label, locked/empty/select/waiting hints,
composer + new-conversation dialog, You / contact request / not-sent tags) to
res/lang/{de,es,fr,ja,ko,pt,ru,zh}.json. Previously they fell back to English.

Added directly to the JSON files (935 -> 950 keys, additive only): the
scripts/gen_<lang>.py generators are stale — they emit ~285 fewer keys than the
committed JSONs, so regenerating from them would silently drop translations.
(Pre-existing issue; noted for follow-up. The generators are left untouched.)

Rebuilt the usage-based CJK subset font (res/fonts/NotoSansCJK-Subset.ttf) from
the full JSONs so the new chat glyphs (聊天 / 对话 / 会話 / 답장, etc.) render —
verified every CJK code point in the full JSONs is covered (no glyph regression).

Verified: Linux + Windows build (embedded lang headers regenerated via xxd, font
re-embedded via INCBIN), hygiene clean; per-file diff is additive (15 keys, 0
deletions).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

res/lang/de.json

@@ -110,6 +110,21 @@
     "bootstrap_warning": "Vorhandene Blockdaten (blocks, chainstate, notarizations) werden gelöscht und ersetzt. Ihre wallet.dat wird NICHT verändert oder gelöscht.",
     "cancel": "Abbrechen",
     "characters": "Zeichen",
+    "chat": "Chat",
+    "chat_cancel": "Abbrechen",
+    "chat_contact_request": "kontaktanfrage",
+    "chat_empty_hint": "Noch keine Unterhaltungen. Nachrichten, die du erhältst, erscheinen hier.",
+    "chat_locked_hint": "Entsperre deine Wallet, um deine Chats zu laden.",
+    "chat_new_button": "Neue Unterhaltung",
+    "chat_new_message": "Nachricht",
+    "chat_new_send": "Anfrage senden",
+    "chat_new_title": "Neue Unterhaltung",
+    "chat_new_zaddr": "z-Adresse des Empfängers",
+    "chat_select_hint": "Wähle eine Unterhaltung aus, um sie anzuzeigen.",
+    "chat_send": "Senden",
+    "chat_send_failed": "nicht gesendet",
+    "chat_waiting_reply": "Warte auf die Antwort dieses Kontakts – sobald er antwortet, kannst du ihm schreiben.",
+    "chat_you": "Du",
     "choose_icon": "Symbol wählen",
     "clear": "Leeren",
     "clear_all_bans": "Alle Sperren aufheben",