[Airdrop P2] Streak check-in system (SIWE)

[realproject7]

Parent: #877
Depends on: #878, #879

Scope

Daily check-in via Sign-In With Ethereum (SIWE). Streak tier applies a multiplier on all other PL earnings (not standalone points).

Streak Tiers

Streak	Boost
0-6 days	+0%
7+ days	+5%
14+ days	+10%
30+ days	+20%
50+ days	+30%
100+ days	+50% (cap)

API

POST /api/airdrop/checkin

Request: SIWE signed message + signature from connected wallet

Logic:

1. Verify SIWE signature → extract wallet address
2. Query pl_streaks for this address
3. Reject if same calendar day (UTC) as last_checkin
4. Reject if last_checkin was less than 30 minutes ago
5. If last_checkin was the previous calendar day → increment current_streak
6. If 2+ days missed → drop one tier:
   • streak 100+ → set to 100
   • streak 50-99 → set to 50
   • streak 30-49 → set to 30
   • streak 14-29 → set to 14
   • streak 7-13 → set to 7
   • streak 1-6 → set to 0
7. Update last_checkin = NOW(), update longest_streak if applicable
8. Return: { streak, boostPercent, nextTier, checkedInToday }

Streak Helper

lib/airdrop/streak.ts:

• getStreakBoost(streak: number): number — returns multiplier (e.g., 0.20 for 30d streak)
• dropOneTier(streak: number): number — returns new streak after one missed day
• getNextTier(streak: number): { days: number, boost: number } | null

Files

• src/app/api/airdrop/checkin/route.ts
• lib/airdrop/streak.ts

Acceptance Criteria

• SIWE signature verified server-side
• One check-in per calendar day (UTC), 30-min minimum gap
• Streak increments on consecutive days
• Missed day drops one tier (not hard reset)
• Streak counter resets to the lower tier's threshold
• Returns current streak + boost % + next tier info
• Boost multiplier used by buy points sync cron ([Airdrop P2] Buy points sync cron #881)