FE: Winner selection + Payout (select-winners signing flow)

[0xdevcollins]

Context

Part of the Bounty Operate to Payout milestone (v1 boundless, Payout). The organizer picks winner(s) per prize tier and triggers the single select_winners op that pushes the reward(s) on-chain. On settle the bounty becomes COMPLETED automatically.

Blueprint to mirror

• Hackathon rewards page: PublishWinnersWizard / AnnouncementStep / PreviewStep; hooks/use-hackathon-publish.ts + features/hackathons/api/use-escrow.ts (useEscrowOpRunner, organizer scope); FundingConfirmationModal / FundingProgressModal.

Tasks

• Winner selection: assign winning submissions to prize positions (1 for single-claim; 1-3 for competition / multiple winners), validate against the bounty's prize tiers + on-chain winner distribution.
• Payout: build the select-winners body (winners: applicantAddress + position), drive useEscrowOpRunner (organizer scope; MANAGED signs server-side, EXTERNAL signs via wallet kit) -> progress modal -> poll to COMPLETED.
• On completion: bounty shows COMPLETED, winners + tx hash surfaced.

Acceptance criteria

• Organizer selects winners and pays out in one signed op; bounty transitions to COMPLETED; payout tx shown. Works for single-winner and multi-winner competitions.

Depends on

• Submissions review; bounty data layer (organizer escrow client select-winners already exists).

[linear]

BOU-286

[Ojas2095]

/claim

I'd like to take this on! Reviewing the repository right now and will submit a PR shortly.

[coderabbitai]

🔗 Related PRs

#438 - Winners tab refactor [merged]
#503 - Feat/improved rewards tab [merged]
#505 - Feat/improved rewards tab [merged]
#576 - fix(rewards): show track winners on the organizer rewards page [merged]
#582 - fix(rewards): match track winners by submissionId, not participantId [merged]

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[Rachaelisa]

/claim #633

Claiming this bounty — going through the codebase now and will open a PR soon.