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.

README.md

@@ -107,9 +107,12 @@ unavailable). The suite lives in `tests/e2e/` and is driven by
 `playwright-core`, whose version must stay matched to the container's Playwright
 version — the browsers ship inside the image.
 
-It covers popup load, wallet creation through the UI, the Add Token screen and
-the transaction detail screen for an ERC-20 transfer. All outbound network is
-intercepted at the browser level and served from fixtures in
+It covers popup load, wallet creation through the UI, the Add Token screen, the
+transaction detail screen for an ERC-20 transfer, and the recovery phrase screen
+— which wallet types are offered it, that it holds nothing before the password
+is accepted, that a wrong password reveals nothing, that leaving it by either
+route wipes it, and that reopening the popup does not land on it. All outbound
+network is intercepted at the browser level and served from fixtures in
 `tests/e2e/network.js`, so the run is deterministic and fully offline;
 unrecognised outbound requests are reported as failures rather than silently
 allowed.
@@ -375,8 +378,11 @@ runtime debug mode is on, or when the active network is a testnet. They are not
 repeated in the element lists below.
 
 Closing and reopening the popup returns to the screen the user was last on only
-for the views listed in `RESTORABLE_VIEWS` (`src/popup/index.js`). Every other
-screen, including ExportPrivKey, falls back to Home.
+for the views listed in `RESTORABLE_VIEWS` (`src/popup/restorableViews.js`).
+Every other screen falls back to Home. The screens that display a secret —
+ExportPrivKey and ShowRecoveryPhrase — are deliberately absent from that list,
+so the popup can never reopen onto one of them with no password prompt in front
+of it.
 
 #### Welcome (`welcome`)
 
@@ -676,8 +682,9 @@ screen, including ExportPrivKey, falls back to Home.
 - **When**: User tapped the Settings gear.
 - **Elements**:
     - "Back" button, "Settings" heading
-    - Wallets: one row per wallet with its name (tap to rename inline) and an
-      `[x]` delete button, plus a "+ Add wallet" button
+    - Wallets: one row per wallet with its name (tap to rename inline), a
+      `[recovery phrase]` button on HD wallets only, and an `[x]` delete button,
+      plus a "+ Add wallet" button
     - Tracked Tokens: one row per tracked token with an `[x]` remove button,
       plus a "+ Add token" button
     - Display: "Show tracked tokens with zero balance" checkbox and a Theme
@@ -702,6 +709,7 @@ screen, including ExportPrivKey, falls back to Home.
 - **Transitions**:
     - "+ Add wallet" → **AddWallet**
     - "+ Add token" → **SettingsAddToken**
+    - `[recovery phrase]` on an HD wallet → **ShowRecoveryPhrase**
     - `[x]` on a wallet → **DeleteWallet**
     - Tap wallet name → inline rename field (no screen change)
     - `[x]` on a tracked token or a site → removes it in place (no screen
@@ -709,6 +717,32 @@ screen, including ExportPrivKey, falls back to Home.
     - Ten clicks on the version → reveals the Debug well (no screen change)
     - "Back" (or Settings gear again) → previous screen (Home)
 
+#### ShowRecoveryPhrase (`show-phrase`)
+
+- **When**: User tapped `[recovery phrase]` on a wallet row in Settings. HD
+  wallets only: key and xprv wallets have no recovery phrase, so their rows do
+  not offer the action at all.
+- **Elements**:
+    - "Back" button, "Recovery Phrase" heading
+    - Wallet name
+    - Warning box stating that anyone holding these words can take everything in
+      the wallet, from any device, without the password
+    - Error line
+    - Password input + "Reveal" button, shown until the password is accepted
+    - The recovery phrase itself, in full and click-to-copy, shown only after a
+      correct password and in place of the password prompt
+- **Transitions**:
+    - "Reveal" (correct password) → the phrase replaces the password prompt (no
+      screen change)
+    - "Reveal" (wrong password) → full-sentence error, nothing revealed (no
+      screen change)
+    - "Back" → previous screen (Settings)
+- **Secret handling**: nothing is decrypted or written into the page until the
+  password is accepted; the phrase is never stored in state, and it is wiped
+  from the page whenever the screen is left by any route, including the Settings
+  gear. The screen is not restorable, so reopening the popup lands on Home
+  rather than back on the phrase.
+
 #### DeleteWallet (`delete-wallet-confirm`)
 
 - **When**: User tapped the `[x]` next to a wallet in Settings.
@@ -1148,7 +1182,7 @@ Currently supported:
 
 - [x] Delete wallet (with confirmation)
 - [ ] Delete address from HD wallet (with confirmation)
-- [ ] Show wallet's recovery phrase (requires password)
+- [x] Show wallet's recovery phrase (requires password)
 
 ### Transactions