fix: resolve token symbols from multiple sources (closes #51)

When tokenBalances doesn't contain an entry for a token (e.g. before
balances are fetched), the symbol fell back to '?' in addressToken
and send views.

Add resolveSymbol() helper that checks tokenBalances → TOKEN_BY_ADDRESS
(known tokens) → trackedTokens → truncated address as last resort.

Fixes USDC and other known tokens showing '?' when balance data
hasn't loaded yet.

src/shared/tokenList.js

@@ -3645,10 +3645,27 @@ async function getTopTokenPrices(n) {
     return prices;
 }
 
+// Resolve a token symbol from multiple sources, never returning "?".
+function resolveSymbol(tokenAddress, tokenBalances, trackedTokens) {
+    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);
+    if (known && known.symbol) return known.symbol;
+    const tracked = (trackedTokens || []).find(
+        (t) => t.address.toLowerCase() === lower,
+    );
+    if (tracked && tracked.symbol) return tracked.symbol;
+    return lower.slice(0, 10) + "\u2026";
+}
+
 module.exports = {
     TOKENS,
     TOKEN_BY_ADDRESS,
     KNOWN_SYMBOLS,
     getTopTokens,
     getTopTokenPrices,
+    resolveSymbol,
 };