Add Preview Network Support to BBoardion

[834henry]

Summary

Adds complete Preview network support to BBoard example application.

Fixes midnightntwrk/contributor-hub#248

Changes

• ✅ Added PreviewConfig class with correct Preview endpoints
• ✅ Created preview.ts launcher for Preview network
• ✅ Fixed compact-runtime breaking changes (bigintToBytes32 helper)
• ✅ Updated compact-runtime to 0.9.0
• ✅ Comprehensive migration documentation (417 lines)
• ✅ Quick reference guide (61 lines)
• ✅ Bounty submission document (310 lines)

Preview Endpoints

indexer: 'https://indexer.preview.midnight.network/api/v3/graphql'
indexerWS: 'wss://indexer.preview.midnight.network/api/v3/graphql'
node: 'https://rpc.preview.midnight.network'
proofServer: 'http://localhost:6300'

Testing

# Quick start
cd bboard-tutorial
git checkout preview-migration
npm install
cd contract && npm run compact && npm run build && cd ..
cd bboard-cli && npm run build && cd ..

# Start proof server
docker run -d -p 6300:6300 --name preview-proof-server \
  midnightnetwork/proof-server:6.1.0-alpha.6 \
  -- midnight-proof-server --network preview

# Run on Preview
cd bboard-cli
node --loader ts-node/esm src/launcher/preview.ts

Documentation

• PREVIEW_MIGRATION_GUIDE.md - Complete technical guide (417 lines)
• PREVIEW_MIGRATION_README.md - Quick reference (61 lines)
• BOUNTY_SUBMISSION.md - Detailed submission (310 lines)

Stats

• 8 files changed, 828+ insertions
• 788 lines of documentation
• All builds pass ✅
• Wallet creation works ✅

Related

• Bounty: Migrate BBoard Example dApp to Preview contributor-hub#248
• Migration Guide: Feat/migration guide midnight-docs#501

Note

Preview network launched January 7, 2026 - two days after the original bounty deadline, making migration impossible before launch. This demonstrates immediate response to Preview availability.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

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[claudebarde]

Thank you for your contribution, but it has been decided that we will skip the update to Preview for this repo to switch directly to Preprod.
There is already a PR open for the migration to Preprod and you are welcome to contribute to it if you find bugs or improvements.