fix(FeeVault): add zero address check in constructor

Prevents deploying the contract with a zero address owner, which would
permanently lock all administrative functions.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: tac0turtle

contracts/src/FeeVault.sol

@@ -45,6 +45,7 @@ contract FeeVault {
         uint256 _bridgeShareBps,
         address _otherRecipient
     ) {
+        require(_owner != address(0), "FeeVault: owner is the zero address");
         require(_bridgeShareBps <= 10000, "FeeVault: invalid bps");
 
         owner = _owner;