Replaced public distribution with winner claim lifecycle

[Birdmannn]

Pull Request Template

Description

feat(giveaway): explicit winner claim flow + edge-case test coverage

Closes #405

Summary

Replaces the push-based prize distribution with an explicit pull-based claim lifecycle and expands test coverage across all claim lifecycle edge cases.

Changes

giveaway.rs

• Added GiveawayPrizeClaimed event emitted on every successful claim_prize call.
  Topics: ["giveaway", "claimed", <winner>] — data: [giveaway_id, net_amount].

test.rs

• Added setup_giveaway_env test helper to reduce boilerplate across new tests.
• Added 20 new tests:

Test	What it covers
test_pick_winner_twice_fails	pick_winner on a Claimable giveaway panics
test_claim_prize_emits_event	GiveawayPrizeClaimed topics and net_amount are correct
test_claim_prize_zero_fee_pays_full_amount	fee_bps=0 — winner receives full gross share
test_claim_prize_full_fee_pays_zero_net	fee_bps=10000 — winner gets 0, contract holds all
test_recover_on_completed_giveaway_fails	Recovery on a Completed giveaway panics
test_recover_after_all_claimed_is_noop	Same panic path when all winners already claimed
test_recover_by_admin_after_expiry_succeeds	Admin (not creator) can call recover_unclaimed_prize
test_claim_at_deadline_boundary	Claim at timestamp == claim_deadline succeeds
test_claim_one_second_past_deadline_fails	Claim at deadline + 1 panics with ClaimWindowExpired
test_status_stays_claimable_after_first_of_two_claims	Status is Claimable after 1st claim, Completed after 2nd
test_winner_gross_share_remainder_distribution	amount=10, 3 winners — index-0 gets 4, 1 and 2 get 3
test_pick_winner_insufficient_participants_fails	participant_count < winner_count panics
test_pick_winner_zero_participants_fails	Zero participants panics with NoParticipants
test_multi_winner_equal_split	400 tokens / 4 winners — each gets exactly 100
test_create_giveaway_zero_winner_count_fails	winner_count=0 panics with InvalidWinnerCount
test_create_giveaway_zero_amount_accepted	amount=0 is stored; zero-prize giveaway is valid
test_recover_unclaimed_returns_full_gross_share_no_fee	Recovery sends full gross share — no fee deducted
test_reputation_not_incremented_on_recovery	Creator reputation stays 0 when recovery (not claim) finalizes
test_manual_winners_non_participant_fails	finalize_manual_winners with an outsider panics
test_manual_winners_duplicate_fails	Duplicate address in manual winner list panics
test_finalize_merit_winners_on_random_giveaway_fails	finalize_merit_winners on a Random giveaway panics

Acceptance criteria

• ✅ Only the selected winner can claim — claim_prize calls winner.require_auth() and validates against the stored winners list
• ✅ Winner selection and payout are separate actions — pick_winner sets Claimable, claim_prize handles the transfer
• ✅ Fee accounting preserved — fees deducted per claim, tracked in CollectedFees
• ✅ Reputation updated — creator rep incremented when the last winner claims

Test results

	Count
Before	97 passing
After	143 passing, 0 failing

CI

• cargo fmt --all -- --check ✅
• cargo clippy --workspace --all-targets --all-features --locked -- -D warnings ✅
• cargo test --workspace --locked ✅
• cargo build --workspace --target wasm32-unknown-unknown --release --locked ✅

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Checklist

• I have tested my changes locally
• I have updated documentation as needed
• I have run npx prisma generate after schema changes
• I have run npx prisma migrate dev or npx prisma migrate deploy as appropriate

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Post-Merge Steps for Maintainers

If this PR includes changes to the Prisma schema:

1. Run the following command to apply the migration to your database:

   npx prisma migrate deploy

   or, for local development:

   npx prisma migrate dev

2. Ensure your CI pipeline runs the migration before tests (add this step if missing):

   - name: Run Prisma Migrate
     run: npx prisma migrate deploy

3. Make sure the database user in CI has permission to run migrations.

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If you have any questions, please comment on this PR.
this PR closes #405