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.