Fold watch-only into Import; support xprv spending import

Home screen is back to two tabs (Create / Import). The Import box now
takes a recovery phrase, an xpub/zpub, or an xprv/zprv:
- mnemonic → full wallet (as before)
- xpub/zpub → watch-only (view/receive, no Send)
- xprv/zprv → full spending wallet with no mnemonic. parseExtendedKey
  classifies + normalizes version bytes; account() derives the BIP84
  path from a master xprv (depth 0) or uses an account-level xprv as-is;
  signing works (only watch-only blocks it). Vault persists xprv accounts
  too; Settings shows an "Imported key" note instead of a recovery card
  and hides Nostr sync (no seed). Public-key export still works.

Note: a seed phrase cannot be derived from an xprv (one-way KDF), so an
xprv wallet has no recovery words by design. New strings in all 19 locales.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

1 files changed, 7 insertions, 2 deletions

diff --git a/src/locales/ja.json b/src/locales/ja.json
index 55ea846..dc6017d 100644
--- a/src/locales/ja.json
+++ b/src/locales/ja.json
@@ -205,5 +205,10 @@
   "unlockSavedDesc": "この端末に保存したウォレットを開くにはパスワードを入力してください。",
   "unlock": "解除",
   "useAnotherWallet": "別のウォレットを使う",
-  "save": "保存"
-}
+  "save": "保存",
+  "importLabel": "復元フレーズまたは鍵",
+  "importPlaceholder": "12 または 24 個の単語、または xpub / xprv",
+  "invalidImport": "有効な復元フレーズ、xpub、xprv ではありません。",
+  "importedKey": "インポートした鍵",
+  "importedKeyNote": "このウォレットは拡張秘密鍵からインポートされたため、復元フレーズはありません。ウォレットを保持するにはその鍵自体をバックアップしてください。"
+}
\ No newline at end of file