fix: the bundled token list names tokens on Ethereum Mainnet only (closes #632)

bundledToken(address, chainId) in tokenList.js answers only for Ethereum
Mainnet's chain id. Every reader of the bundled list now goes through it,
with the chain id of the transaction, balance or history entry it draws.
The token sources the screens build carry that chain id. The Uniswap
decoder sets the transaction's chain id on them. fetchTokenBalances()
takes the chain id of the network it asks about.

Seven existing tests read the bundled list without naming a network. Each
now names Ethereum Mainnet.

Model: opus-5-5

tests/holders.test.js

@@ -192,7 +192,13 @@ describe("the balance-list spam gate", () => {
                 },
             }),
         ]);
-        const balances = await fetchTokenBalances(HOLDER, BLOCKSCOUT, []);
+        // On Ethereum Mainnet, the only network the known-token list covers.
+        const balances = await fetchTokenBalances(
+            HOLDER,
+            BLOCKSCOUT,
+            [],
+            "0x1",
+        );
         expect(balances).toHaveLength(1);
         expect(balances[0].holders).toBeNull();
     });