Implement dispute resolution mechanism for milestones

[0xdevcollins]

Problem

dispute_milestone() sets milestone status to Disputed but there is no resolution mechanism. Disputed milestones become a dead-end with no way to resolve them in favor of either party.

Current Behavior

• Backer calls dispute_milestone() → milestone status becomes Disputed
• No function exists to resolve the dispute
• No emergency refund if dispute is resolved in backer's favor
• No reputation penalty for failed disputes

Expected Behavior

Add dispute resolution functions:

Contract Changes

1. resolve_dispute(campaign_id, milestone_index, resolution: DisputeResolution) (Admin-only)
   • DisputeResolution::ApproveCreator → milestone status back to Submitted or Released (release funds)
   • DisputeResolution::ApproveBacker → milestone status to Rejected, trigger partial refund or hold
2. get_dispute_status(campaign_id, milestone_index) — query current dispute state
3. Emit DisputeResolved event with resolution details

Acceptance Criteria

• Admin can resolve disputes in favor of creator or backer
• Funds are handled correctly based on resolution outcome
• Events emitted for indexer to pick up
• Tests cover both resolution paths

Priority

High — This is a critical gap in the end-to-end flow. Backers can file disputes but nothing happens.

Labels

crowdfunding, smart-contract, critical