feat(board): Lightning-paid message board with LNbits and admin moderation

Add public /board flow: create invoice, webhook + confirm reconciliation, list
active messages, likes (Nostr), zap fallbacks. Admin table for hide/delete.

Include LNbits webhook body normalization (double-encoded JSON), POST
/api/messages/confirm/:hash, and root npm db:push script. Prisma models for
pending invoices and board messages.

Made-with: Cursor

.env.example

@@ -4,7 +4,9 @@ ADMIN_PUBKEYS=npub1examplepubkey1,npub1examplepubkey2
 # Nostr relays (comma-separated)
 RELAYS=wss://relay.damus.io,wss://nos.lol,wss://relay.nostr.band
 
-# Database (use an absolute `file:` URL in production, e.g. file:/home/bbe/BelgianBitcoinEmbassy/backend/prisma/prod.db)
+# Database (path is relative to backend/prisma/ when using file: URLs — see Prisma docs)
+# Apply schema: from repo root run `npm run db:push`, or from backend run `npm run db:push`.
+# Do not run bare `npx prisma db push` from the repo root (no schema there; wrong Prisma version).
 DATABASE_URL="file:./dev.db"
 
 # JWT
@@ -22,3 +24,15 @@ NEXT_PUBLIC_API_URL=http://localhost:4000/api
 NEXT_PUBLIC_SITE_URL=https://belgianbitcoinembassy.org
 NEXT_PUBLIC_SITE_TITLE=Belgian Bitcoin Embassy
 NEXT_PUBLIC_SITE_TAGLINE=Belgium's Monthly Bitcoin Meetup
+
+# Message board (Lightning / LNbits) — backend
+MESSAGE_PRICE_SATS=1000
+LNBITS_API_KEY=
+LNBITS_WEBHOOK_SECRET=
+LNBITS_URL=https://legend.lnbits.com
+# Public URL that LNbits can POST webhooks to (usually your site origin so /api/messages/webhook hits the API)
+WEBHOOK_BASE_URL=http://localhost:3000
+# Optional: lnaddress or LNURL-pay string for “Zap BBE” when the message has no pubkey
+BOARD_ZAP_LN_ADDRESS=
+# Optional: hex pubkey for njump fallback when BOARD_ZAP_LN_ADDRESS is unset
+BOARD_ZAP_PUBKEY=