Pull cyToken `symbol` from on-chain instead of canonical JSON

Each entry in `cyclo.sol/canonical/cyclo-site-tokens.json` carries the vault's `symbol` as a hardcoded string. The vault is an ERC20 with a `symbol()` accessor — read it via `readContract` keyed by `(chainId, vaultAddress)`, cache, and drop the `symbol` field from the canonical JSON. Used by the dropdown labels and the `balancesStore.balances[token.name]` keying logic — the `name` to `symbol` mapping needs review when this lands.

Start with cyclo.sol/canonical/cyclo-site-tokens.json and the code that calls readContract for (chainId, vaultAddress), then trace the dropdown labels and balancesStore.balances[token.name] keying logic. Done means symbols are read and cached by chainId and vaultAddress, the JSON symbol field is removed, and the name-to-symbol mapping still works.

Written by the indexing model from the issue text.