feat(history): badge chat transactions + add a Chat filter

Transactions that carried a chat message (sent or received, messages + contact
requests) now show a "Message" badge in the History tab, and a new "Chat" option
in the type-filter combo shows only those transactions.

Detection reuses what the chat store already tracks: ChatStore gains an inline
chatTxids() returning the set of on-chain txids that carried a chat message; the
tab builds it once per frame (cheap — O(chat messages)) and tests txid membership
for the badge and the filter. Empty when chat is disabled or the wallet has no
chat identity. Both variants populate the chat store before this tab renders, so
the same code serves full-node and lite with no separate handling.

The "Message" badge reuses the stacked top-pill slot (chat txs are send/receive,
not the autoshield "shield" type, so it and the "Shielded" badge are mutually
exclusive; chat takes precedence) in a distinct Secondary() colour. Guards the
summary-card accent idx_map so the new filter value (4) can't index it OOB.

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

res/lang/ko.json

@@ -167,6 +167,7 @@
     "chat_export_done": "대화를 내보냈습니다",
     "chat_export_failed": "내보내기 파일을 쓸 수 없습니다.",
     "chat_export_warn": "복호화된 메시지를 일반 텍스트로 저장합니다. 파일을 안전하게 보관하세요.",
+    "chat_filter": "채팅",
     "chat_hidden_toast": "대화를 숨겼습니다 — 새 메시지가 오면 다시 표시됩니다",
     "chat_hide": "숨기기",
     "chat_hide_hidden": "숨김 접기",
@@ -1526,6 +1527,7 @@
     "tt_website": "DragonX 웹사이트 열기",
     "tt_window_opacity": "배경 불투명도 (낮을수록 = 창을 통해 바탕 화면이 보임)",
     "tt_wizard": "초기 설정 마법사 다시 실행\\n데몬이 재시작됩니다",
+    "tx_chat_badge": "메시지",
     "tx_confirmations": "%d 확인",
     "tx_details_title": "거래 상세",
     "tx_from_address": "보낸 주소:",