feat(CHAIN-4707): add Zeronet SystemConfig ownership transfer task

[0xth4nh]

Summary

Adds a Zeronet signing task (CHAIN-4707) that transfers ownership of the Zeronet SystemConfig proxy from the proxy admin owner Safe to the incident multisig.

Ownership currently lives with the nested proxy admin owner Safe. The task follows the existing nested Safe flow: Coinbase and Security Council signers approve the nested transaction hash, then the proxy admin owner Safe executes one SystemConfig.transferOwnership call.

Owners

Role	Address
Current owner (proxy admin owner)	0x3d59999977e0896ee1f8783bB8251DF16fb483E9
New owner (incident multisig)	0x856611ed7e07d83243b15e93f6321f2df6865852

Transfer (1 call)

Contract	Mechanism
SystemConfig	transferOwnership

The script validates the current owner before building the call and validates owner() equals the incident multisig in the post-check.

[linear]

CHAIN-4707

[cb-heimdall]

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