fix(wallet-switch): cluster C — no mis-scoping in the unknown-identity window

From the audit: while a switch/first-load is in flight the wallet identity hash
is empty, so contact/portfolio scope-writes silently fell back to "global"
(leaking a wallet-specific entry into every wallet) and scope-filters showed
every wallet's scoped entries.

- Contacts: a NEW wallet-scoped contact created while the identity is unknown is
  now refused with a clear message (tick global or wait); editing an existing
  scoped contact preserves its scope instead of demoting it to global.
- Portfolio: the "Add group" button is disabled while the identity is unknown
  (with a tooltip), so a new group can't get an empty/global scope.
- Both views' visibility filters now show ONLY global entries when the identity
  is unknown — never another wallet's scoped contacts/groups — instead of
  showing everything.
- +2 i18n strings (8 langs; reworded one zh string to stay within the CJK subset).

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

res/lang/ko.json

@@ -305,6 +305,7 @@
     "contact_global_tt": "켜짐: 어떤 지갑을 불러오든 이 연락처가 계속 표시됩니다. 꺼짐: 현재 지갑에만 속합니다.",
     "contact_preview_addr": "여기에 주소가 표시됩니다",
     "contact_preview_name": "연락처 이름",
+    "contact_wallet_loading": "지갑을 아직 불러오는 중입니다 — “모든 지갑에 표시”를 선택하거나 잠시 후 다시 시도하세요.",
     "contacts": "연락처",
     "contacts_search_no_match": "일치하는 연락처 없음",
     "contacts_search_placeholder": "연락처 검색...",
@@ -977,6 +978,7 @@
     "portfolio_style_featured": "강조 행",
     "portfolio_style_label": "포트폴리오 스타일",
     "portfolio_untitled": "제목 없음",
+    "portfolio_wallet_loading": "지갑 로딩이 끝난 후 그룹을 추가하세요.",
     "price_chart": "가격 차트",
     "privacy_great": "프라이버시가 우수합니다!",
     "privacy_low": "낮은 프라이버시 — 자금을 차폐하세요",