Full policy-management dashboard (create/update/revoke)

[Alhaji-naira]

Summary

Extend the read-only dashboard into a write-capable UI: connect a wallet (e.g. Freighter), create/update/revoke policies, and visualize window usage over time. Handle the owner-vs-agent signer distinction cleanly.

Acceptance criteria

• An owner can manage a policy end-to-end from the UI on Testnet
• Signing goes through a wallet, never raw secrets
• Usage-over-time visualization