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

src/shared/tokenList.js

@@ -3953,6 +3953,15 @@ for (const t of TOKENS) {
     TOKEN_BY_ADDRESS.set(t.address.toLowerCase(), t);
 }
 
+// The bundled list's entry for the contract at `address` on the network with
+// chain id `chainId`, or null. The list holds Ethereum Mainnet contracts only.
+// A contract at the same address on another network is another token, so any
+// other chain id gets null.
+function bundledToken(address, chainId) {
+    if (chainId !== NETWORKS.mainnet.chainId) return null;
+    return TOKEN_BY_ADDRESS.get((address || "").toLowerCase()) || null;
+}
+
 // Build a map of symbol (uppercased) -> the set of contract addresses
 // (lowercased) that legitimately bear it.  Used for spoofed-symbol detection.
 // "ETH" maps to null: the native asset has no contract, so no contract may
@@ -3988,14 +3997,15 @@ for (const t of TOKENS) {
     }
 }
 
-// Resolve a token symbol from multiple sources, never returning "?".
-function resolveSymbol(tokenAddress, tokenBalances, trackedTokens) {
+// Resolve a token symbol from multiple sources, never returning "?". The token
+// is a contract on the network with chain id `chainId`.
+function resolveSymbol(tokenAddress, tokenBalances, trackedTokens, chainId) {
     const lower = (tokenAddress || "").toLowerCase();
     const tb = (tokenBalances || []).find(
         (t) => t.address.toLowerCase() === lower,
     );
     if (tb && tb.symbol) return tb.symbol;
-    const known = TOKEN_BY_ADDRESS.get(lower);
+    const known = bundledToken(lower, chainId);
     if (known && known.symbol) return known.symbol;
     const tracked = (trackedTokens || []).find(
         (t) => t.address.toLowerCase() === lower,
@@ -4012,5 +4022,6 @@ module.exports = {
     USD_PRICE_FEEDS,
     PRICE_FEED_BY_ADDRESS,
     getTopTokens,
+    bundledToken,
     resolveSymbol,
 };