Unmintable Token Supply Renders Contract Non-Functional
The `ERC20` contract lacks any mechanism to mint new tokens or set an initial supply. The `_totalSupply` variable is private and never increased, and there is no `_mint` function or constructor logic to populate `_balances`. Consequently, `_totalSupply` will always be zero, and all account balances (`_balances`) will remain zero. Any attempt to `transfer` or `transferFrom` an `amount` greater than zero will revert due to `fromBalance >= amount` check failing, making the token completely unusable.