feat: password-gated recovery phrase display for HD wallets (closes #161)

A user who created a wallet in AutistMask and did not write the phrase
down had no way to retrieve it. Adds a "Show recovery phrase" action on
the wallet row in Settings, next to the per-wallet actions that already
live there, mirroring the per-address private key export in structure,
password gate and warning treatment.

The screen displays the secret that owns every address in the wallet, so:

  - Only HD wallets are offered it. walletHasRecoveryPhrase() is an
    allowlist on type "hd", so the key and xprv types — which have no
    phrase at all — are excluded, as is any type added later.
  - Nothing is decrypted and nothing enters the page until
    decryptWithPassword accepts the password. A wrong password produces a
    full-sentence error and leaves the value node empty.
  - Leaving the screen wipes it by any route, not just "Back": views that
    hold a secret register a cleanup with showView() via onViewLeave(),
    which also covers the settings gear.
  - The phrase is never assigned to state, so it cannot be persisted, and
    the view is not in RESTORABLE_VIEWS — reopening the popup lands on
    Home. That set moves to src/popup/restorableViews.js so the exclusion
    can be asserted directly; the popup entry point cannot be required
    outside a browser.
  - The phrase cannot reach the logger: the view does not import
    src/shared/log.js, and the failed-decrypt path reports a fixed
    sentence rather than the caught error.

Tests: unit coverage for the type gate, the RESTORABLE_VIEWS exclusion
and the absence of any logger path; the DOM behaviour is driven against
the real popup in the e2e suite, which is where this repo tests views.

tests/e2e/harness.js

@@ -255,6 +255,11 @@ async function openPopup(ctx, popupUrl) {
 
 // Full wallet creation through the real UI: BIP-39 generation, libsodium
 // vault encryption and extension storage persistence, for real.
+//
+// Returns the recovery phrase it generated. Tests that assert on a secret
+// need the real value — checking for "some 12 words" would pass against the
+// wrong wallet's phrase, and checking for nothing at all would pass against
+// a screen that shows the phrase it was supposed to hide.
 async function createWallet(page) {
     await page.click("#btn-welcome-add");
     await visible(page, "#view-add-wallet");
@@ -263,10 +268,12 @@ async function createWallet(page) {
         const el = document.getElementById("wallet-mnemonic");
         return el && el.value.trim().split(/\s+/).length >= 12;
     });
+    const phrase = (await page.inputValue("#wallet-mnemonic")).trim();
     await page.fill("#add-wallet-password", PASSWORD);
     await page.fill("#add-wallet-password-confirm", PASSWORD);
     await page.click("#btn-add-wallet-confirm");
     await visible(page, "#view-main", 60000);
+    return phrase;
 }
 
 // Reach the address detail screen from wherever the popup restored to.
@@ -281,6 +288,7 @@ async function openAddressDetail(page) {
 }
 
 module.exports = {
+    PASSWORD,
     createWallet,
     launch,
     openAddressDetail,