feat: 4055 Implement Owner Management for Smart Contracts

[nosid91]

Description

This PR implements a secure mechanism to transfer and manage the OWNER role in Guardian smart contracts to address security audit findings (#4055).

• Add two-step ownership transfer pattern in Access.sol (proposeOwner, claimOwner, removeOwner)
• Add Guardian CLI commands for owner management (propose-owner, claim-owner, remove-owner)
• Add comprehensive test suite for ownership transfer scenarios
• Document owner management workflow in contracts README

Related issue(s)

Fixes #4055

Notes for Reviewer

Why Two-Step Ownership Transfer?

The implementation uses a two-step ownership transfer pattern (propose + claim) instead of direct transfer for the following security reasons:

1. Prevents accidental transfers: Direct ownership transfer to an incorrect address (typos, copy-paste errors) would result in permanent loss of contract control. The two-step pattern requires the new owner to actively claim ownership, confirming they have access to the destination address.

2. Validates recipient capability: The claim step verifies that the new owner can actually execute transactions, ensuring they have the private key and proper account setup.

3. Provides recovery window: If an owner accidentally proposes the wrong address, they can simply propose a different address to overwrite the pending owner before the claim occurs.

4. Industry standard: This pattern is widely adopted in production contracts (OpenZeppelin's Ownable2Step, major DeFi protocols) as a security best practice.

Security Constraints

• Owners cannot remove themselves (prevents accidental lockout)
• Contract address cannot be removed as owner (maintains internal call capability)
• pendingOwner is cleared after successful claim (prevents replay)

Backwards Compatibility

• Existing deployed contracts are not affected
• No changes to existing public interfaces

Checklist

• Documented (Code comments, README, CLI help)
• Tested (integration tests with Hedera local node)