refactor: unify add-wallet, import-key, and import-xprv into single view

Merge all three wallet import methods (recovery phrase, private key,
extended key/xprv) into one tabbed add-wallet view with a mode selector.
This fixes the blank import-xprv render (it was missing from the VIEWS
array) and the broken back-button navigation from the separate import
views.

- Add tab selector: Recovery Phrase | Private Key | Extended Key (xprv)
- Share password fields across all modes
- Remove separate import-key and import-xprv views and modules
- Add duplicate wallet detection for private key imports
- All tabs follow affordance policy (visible border + hover state)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/popup/index.js

@@ -10,8 +10,6 @@ const { $, showView } = require("./views/helpers");
 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");
@@ -55,8 +53,6 @@ const ctx = {
     renderWalletList,
     doRefreshAndRender,
     showAddWalletView: () => addWallet.show(),
-    showImportKeyView: () => importKey.show(),
-    showImportXprvView: () => importXprv.show(),
     showAddressDetail: () => addressDetail.show(),
     showAddressToken: () => addressToken.show(),
     showAddTokenView: () => addToken.show(),
@@ -219,8 +215,6 @@ async function init() {
 
     welcome.init(ctx);
     addWallet.init(ctx);
-    importKey.init(ctx);
-    importXprv.init(ctx);
     home.init(ctx);
     addressDetail.init(ctx);
     addressToken.init(ctx);