feat: add xprv wallet import support

Add the ability to import an existing HD wallet using an extended
private key (xprv) instead of a mnemonic phrase.

- New 'xprv' wallet type with full HD derivation and address scanning
- New importXprv view with password encryption
- Updated getSignerForAddress to handle xprv wallet type
- Added xprv link to the add-wallet view
- Allow adding derived addresses for xprv wallets

Closes #20

src/popup/index.js

@@ -11,6 +11,7 @@ const home = require("./views/home");
 const welcome = require("./views/welcome");
 const addWallet = require("./views/addWallet");
 const importKey = require("./views/importKey");
+const importXprv = require("./views/importXprv");
 const addressDetail = require("./views/addressDetail");
 const addressToken = require("./views/addressToken");
 const send = require("./views/send");
@@ -55,6 +56,7 @@ const ctx = {
     doRefreshAndRender,
     showAddWalletView: () => addWallet.show(),
     showImportKeyView: () => importKey.show(),
+    showImportXprvView: () => importXprv.show(),
     showAddressDetail: () => addressDetail.show(),
     showAddressToken: () => addressToken.show(),
     showAddTokenView: () => addToken.show(),
@@ -218,6 +220,7 @@ async function init() {
     welcome.init(ctx);
     addWallet.init(ctx);
     importKey.init(ctx);
+    importXprv.init(ctx);
     home.init(ctx);
     addressDetail.init(ctx);
     addressToken.init(ctx);