forc deploy with [proxy] reuses the same address across networks (testnet → mainnet), causing deploy failure

### Related Component

forc-deploy

### Problem you are trying to solve

When [proxy] is enabled in forc.toml, doing a testnet/mainnet deploy writes a proxy address into the config. A subsequent alternate deploy reuses that same proxy address, which doesn’t exist on the other network, so the deploy fails. This makes multi-network workflows fragile and forces manual edits to forc.toml between deploys.

### Solution you'd like

[proxy]
enabled = true

[proxy.addresses]
testnet = "0x_testnet_proxy"
mainnet = "0x_mainnet_proxy"

### Notes

_No response_