feat(wallet): new/import wallets + multi-wallet i18n (P3)

Completes the wallet-files dialog and localizes the feature.

- Create a new wallet: a name is normalized to wallet-<name>.dat and opened
  via switchToWallet; the daemon mints it (seed-backed, -usemnemonic=1) on
  first load. Rejects blank names + name collisions.
- Import: out-of-datadir wallets get an Import action that copies the file
  into the datadir (never overwriting) under a wallet-*.dat name, then opens
  it — the daemon only loads plain filenames from the datadir.
- i18n: the 32 new multi-wallet / per-wallet-contacts / mining-payout strings
  translated into all 8 languages (de/es/fr/ja/ko/pt/ru/zh), CJK subset font
  rebuilt. Verified: the Chinese Wallets dialog renders with no missing glyphs.

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

src/app_sweep.cpp

@@ -282,6 +282,12 @@ void App::buildSweepCatalog()
                 e2.lastOpenedEpoch = 1719400000; e2.syncedHere = true;
                 a.walletIndex().upsert(e1);
                 a.walletIndex().upsert(e2);
+                // An out-of-datadir wallet (in an extra folder) so the Import action shows too.
+                const std::string extra = util::Platform::getConfigDir() + "extra-wallets";
+                fs::create_directories(extra, ec);
+                if (!fs::exists(extra + "/my-wallet.dat", ec))
+                    std::ofstream(extra + "/my-wallet.dat", std::ios::binary) << std::string(80000, '\0');
+                a.walletIndex().addExtraFolder(extra);
                 if (a.settings()) a.settings()->setActiveWalletFile("wallet.dat");
                 ui::WalletsDialog::show(&a);
             },