Multi-sig admin for emergency & governance controls

[DevMuhdishaq]

Description
Critical admin actions (pause, migrate, param changes) currently rely on a single admin key. Add M-of-N multi-sig approval, complementing the existing governance_multisig_tests scaffolding.

Direction

• Add a multi-sig config in governance_system/admin: set of signer addresses + threshold.
• Sensitive actions create a pending proposal; signers call approve_action(action_id); execution requires ≥ threshold approvals.
• Reuse nonce for replay protection and events for ProposalCreated/Approved/Executed.

Acceptance criteria

• Action executes only after threshold approvals from distinct signers.
• Below-threshold execution attempts reject.
• Duplicate approval from the same signer counts once.
• Non-signer approval rejects.
• Tests cover 2-of-3 and 3-of-3 configurations.

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[m-hajjo]

Hello Maintainer!!
I am a software engineer and an open source contributor. I would like to work on this issue please

[grantfox-oss]

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Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #216)
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[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign | FWC26 campaign!

@m-hajjo's PR #240 was approved and merged by @DevMuhdishaq.

🏆 @m-hajjo: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (191 total points). Track your full progress on GrantFox.

👏 Great work, @m-hajjo! Keep contributing to StelTade.