[Airdrop P2] Buy points sync cron

[realproject7]

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

Scope

New Vercel cron that syncs trade_history → pl_points for buy events within the campaign window.

Logic

1. Query trade_history for event_type = 'mint' where block_timestamp is within campaign window
2. Filter out ZAP_PLOTLINK address (self-mints via zap contract)
3. For each unprocessed trade:
   • Compute points: reserve_amount converted to PLOT (1 PL per 1 PLOT spent)
   • Look up user's current streak tier from pl_streaks → apply boost multiplier
   • Insert pl_points row with action = 'buy', boosted points, metadata = { trade_id }
4. Check if buyer has a referrer in pl_referrals:
   • If yes: insert action = 'referral' points (20% of buyer's buy points, also boosted by referrer's streak) for the referrer
5. Dedup via metadata->>'trade_id' — skip if already processed

Endpoint

POST /api/cron/airdrop-points

Schedule: Every 5 min (*/5 * * * *)
Auth: CRON_SECRET header (same pattern as existing crons)

Existing Infrastructure

• trade_history table already populated by src/app/api/cron/trade-history/route.ts (every 5 min)
• ZAP_PLOTLINK address defined in lib/contracts/constants.ts
• Streak boost lookup from lib/airdrop/streak.ts (see [Airdrop P2] Streak check-in system (SIWE) #882)

Files

• src/app/api/cron/airdrop-points/route.ts
• lib/airdrop/points.ts (helper: compute points with boost)

Acceptance Criteria

• Cron syncs mint events from trade_history to pl_points
• Points = PLOT spent × streak boost multiplier
• Referral points (20%) inserted for referrer when applicable
• ZAP_PLOTLINK trades filtered out
• Idempotent — re-running doesn't create duplicates
• Only processes trades within campaign window
• Campaign end check — no points after CAMPAIGN_END