[Airdrop P4] Daily price snapshot cron

[realproject7]

Parent: #877
Depends on: #878

Scope

Daily cron job that records PLOT USD price, supply, and mcap for TWAP calculation.

Logic

1. Fetch PLOT USD price via getPlotUsdPrice() (existing in lib/usd-price.ts)
2. Fetch circulating supply from MCV2 Bond or Mint Club SDK
3. Compute mcap = price × supply
4. Insert into pl_daily_prices (date-unique — skip if today already has an entry)

Error handling: If getPlotUsdPrice() returns null (all 3 sources failed), skip the day's snapshot — do NOT insert a zero or stale value. The TWAP calculation at campaign end uses AVG() over available days, so a missing day is better than a wrong value. Log the failure for monitoring.

Endpoint

POST /api/cron/airdrop-price

Schedule: Once/day at midnight UTC (0 0 * * *)
Auth: CRON_SECRET header

TWAP Usage

At campaign end, the final milestone is determined by the 7-day TWAP:
AVG(mcap_usd) FROM pl_daily_prices WHERE recorded_at >= (end_date - 7 days)

Files

• src/app/api/cron/airdrop-price/route.ts

Acceptance Criteria

• Records daily PLOT price + supply + mcap
• Idempotent — one entry per day
• Uses existing getPlotUsdPrice() (no new price source)
• Skips snapshot if price fetch fails (no zero/stale values)
• Logs failure when price fetch returns null
• Registered in vercel.json crons (see [Airdrop P4] Weekly stats snapshot cron + vercel.json #891)