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 for history
and token lookups. It sent each recipient to Etherscan for its label. Two
settings, "Use Blockscout" and "Check recipients on Etherscan", now gate those
requests where they are made. 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 naming the setting. Unticking "Use Blockscout"
drops every untracked token from every address. After either changes in
Settings, Back draws again any screen a reopened popup can draw. ENS lookups
ask only the RPC endpoint.

Model: opus-5-5

tests/tokenTransferDetail.test.js

@@ -158,6 +158,7 @@ beforeEach(() => {
     globalThis.document = makeDocument();
     globalThis.window = { location: { search: "" } };
     state.blockscoutUrl = EXPLORER;
+    state.useBlockscout = true;
     state.networkEndpoints = {};
     state.wallets = [
         {
@@ -177,6 +178,7 @@ test("a token transfer's decoded details name the token contract and the amount
     const [row] = await fetchRecentTransactions(
         HOLDER,
         EXPLORER,
+        true,
         NETWORKS.mainnet.chainId,
     );
     expect(row.to).toBe(RECIPIENT);
@@ -209,6 +211,7 @@ test("with mainnet active, a Sepolia transaction is read from Sepolia's Blocksco
     const [row] = await fetchRecentTransactions(
         HOLDER,
         EXPLORER,
+        true,
         NETWORKS.sepolia.chainId,
     );
 
@@ -237,6 +240,7 @@ test("with mainnet active and no Blockscout remembered for Sepolia, a Sepolia tr
     const [row] = await fetchRecentTransactions(
         HOLDER,
         EXPLORER,
+        true,
         NETWORKS.sepolia.chainId,
     );
     mockAsked.length = 0;
@@ -258,6 +262,7 @@ async function showSepoliaTransferWithMainnetActive() {
     const [row] = await fetchRecentTransactions(
         HOLDER,
         EXPLORER,
+        true,
         NETWORKS.sepolia.chainId,
     );
     transactionDetail.show(row);