fix: Blockscout and Etherscan lookups are off until the user turns them on (closes #668)

Out of the box the wallet sent the user's addresses to Blockscout and each
recipient to Etherscan. Two settings, "Use Blockscout" and "Check recipients on
Etherscan", now gate those requests. Both are off in a new install and offered
unticked on Welcome and in Settings. While one is off, the screens that relied
on it say so in a plain line. Each gated request reads its setting from storage
before it asks and when the answer lands, and drops a late answer. An open popup
takes another page's change and draws its screens again. While "Use Blockscout"
is off, no address keeps an untracked token, and no screen names a token from
Blockscout's report. ENS lookups ask only the RPC endpoint.

Model: opus-5-5

tests/stateRecovery.test.js

@@ -523,13 +523,15 @@ describe("a garbage value in a field the gate does not check", () => {
     });
 
     test("a malformed tokenBalances entry is dropped, and the wallet and its address survive", async () => {
-        const env = await bootPopup(
-            profileWithTokenBalances([
-                null,
-                42,
-                { address: TOKEN_ADDRESS, symbol: "AAA", balance: "2.0" },
-            ]),
-        );
+        // "Use Blockscout" is on, or the boot's balance refresh drops the
+        // well-formed entry too: the user has not tracked its token.
+        const profile = profileWithTokenBalances([
+            null,
+            42,
+            { address: TOKEN_ADDRESS, symbol: "AAA", balance: "2.0" },
+        ]);
+        profile.useBlockscout = true;
+        const env = await bootPopup(profile);
 
         const stored = env.storage.read("autistmask");
         expect(stored.wallets[0].encryptedSecret).toBe("encrypted-secret-1");