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, 5 insertions, 0 deletions

diff --git a/src/i18n.js b/src/i18n.js
index 9a48796..0615ec9 100644
--- a/src/i18n.js
+++ b/src/i18n.js
@@ -92,6 +92,11 @@ const STR = {
     show: 'Show',
     hide: 'Hide',
     invalidSeed: 'Invalid seed phrase — check the spelling and word order.',
+    importLabel: 'Recovery phrase or key',
+    importPlaceholder: 'Your 12 or 24 words, or an xpub / xprv',
+    invalidImport: 'That is not a valid recovery phrase, xpub, or xprv.',
+    importedKey: 'Imported key',
+    importedKeyNote: 'This wallet was imported from an extended private key, so there is no recovery phrase. Back up that key itself to keep the wallet.',
     keysNote: 'Keys never leave your browser. Works fully offline. Save this page and open it from your filesystem.',
     howItWorks: 'How it works',
     installApp: 'Install app',