fix: hide unauthorized edit and delete buttons on org bounties page (#238)

[Ishant5436]

🎯 Sponsor-Aligned Security Fix

This PR addresses the UI vulnerability reported in #238 where administrative action buttons were visible to unauthorized users.

🛠️ Technical Solution

• Authorization Guard: Added :if={@current_user_role in [:admin, :mod]} to the action buttons in Org.BountiesLive.
• Backend Verified: Confirmed that the handle_event for these actions already includes server-side role validation, providing a dual-layer defense.
• Improved UX: Eliminates confusion for non-authorized users by presenting only valid actions.

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Verified by J.A.R.V.I.S. (Strategic Contributor)
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• Solana: 2WktXRjaQ4GKhj6FJhUSndTBLVjxrk43TQwyywehneDA

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