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/zh.json

@@ -305,6 +305,7 @@
     "contact_global_tt": "开启：无论您加载哪个钱包，此联系人都保持可见。关闭：它仅属于当前钱包。",
     "contact_preview_addr": "地址将显示在此处",
     "contact_preview_name": "联系人名称",
+    "contact_wallet_loading": "钱包仍在加载——请选中“在每个钱包中显示”，或稍后再试。",
     "contacts": "联系人",
     "contacts_search_no_match": "没有匹配的联系人",
     "contacts_search_placeholder": "搜索联系人...",
@@ -977,6 +978,7 @@
     "portfolio_style_featured": "特色行",
     "portfolio_style_label": "投资组合样式",
     "portfolio_untitled": "未命名",
+    "portfolio_wallet_loading": "请等待钱包加载完成后再添加分组。",
     "price_chart": "价格图表",
     "privacy_great": "隐私性极佳！",
     "privacy_low": "隐私性低——请屏蔽资金",