Handle vote rejection path in check_vote_threshold

[0xdevcollins]

Problem

check_vote_threshold() only handles the "Approve" path (option 0). If community voters choose "Reject" (option 1), the campaign stays in Submitted status forever — there is no explicit rejection handling.

Current Behavior

vote_campaign(voter, campaign_id, option_id=1)  // Vote "Reject"
check_vote_threshold(campaign_id)               // Fails with VoteThresholdNotMet
// Campaign stuck in Submitted forever

Expected Behavior

check_vote_threshold should:

1. Check if voting period has ended
2. If "Approve" threshold met → transition to Campaigning (existing behavior)
3. If "Reject" threshold met OR voting period expired without approval → transition back to Draft with reason
4. Emit CampaignVoteRejected event

Acceptance Criteria

• Campaigns rejected by community vote return to Draft status
• Creator is notified (via event) that their campaign was voted down
• Voting session is cleaned up after rejection
• Tests cover: approve path, reject path, expired-without-quorum path

Priority

High — Without this, rejected campaigns are orphaned forever.

Labels

crowdfunding, smart-contract, bug