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/ja.json

@@ -305,6 +305,7 @@
     "contact_global_tt": "オン：この連絡先はどのウォレットを読み込んでも表示されます。オフ：現在のウォレットにのみ属します。",
     "contact_preview_addr": "ここにアドレスが表示されます",
     "contact_preview_name": "連絡先名",
+    "contact_wallet_loading": "ウォレットを読み込み中です。「すべてのウォレットに表示」にチェックするか、少し待ってから再試行してください。",
     "contacts": "連絡先",
     "contacts_search_no_match": "一致する連絡先がありません",
     "contacts_search_placeholder": "連絡先を検索...",
@@ -977,6 +978,7 @@
     "portfolio_style_featured": "注目行",
     "portfolio_style_label": "ポートフォリオスタイル",
     "portfolio_untitled": "無題",
+    "portfolio_wallet_loading": "ウォレットの読み込みが終わってからグループを追加してください。",
     "price_chart": "価格チャート",
     "privacy_great": "優れたプライバシーです！",
     "privacy_low": "プライバシーが低い — 資金をシールドしてください",