feat: eliminate sender flag if account

[zjesko]

solves #10632

Primary Enhancement

Make --sender optional when --account is specified. Foundry should automatically derive the sender address from the account's private key.

Desired Usage

# Simple case - sender automatically derived from account
forge script script/Deploy.s.sol --rpc-url unichain --account deployer --broadcast

Implementation Logic

1. When --account is provided without --sender:

• Load the specified account from the keystore
• Derive the address from the private key
• Use that address as the sender for transactions
• Set msg.sender appropriately in the script context

2. When both --account and --sender are provided:

• Validate that the sender address matches the account's derived address
• Throw a clear error if there's a mismatch
• This maintains backward compatibility for existing scripts

3. When only --sender is provided (current behavior):

• Continue to work as before for raw private key workflows
• Maintain full backward compatibility

[zjesko]

solves #10632

please have a look @zerosnacks @grandizzy @mattsse

[mshakeg]

nice! lgtm