feat(infra): add Heroku deployment configuration

[mroderick]

Summary

Add Heroku infrastructure-as-code configuration for deploying codebar-auth to Heroku with automatic deployments from GitHub.

Changes

• app.json: Heroku app manifest with PostgreSQL Essential-0, Basic dyno, and environment variables
  • CODEBAR_AUTH_URL set to https://auth.codebar.io
  • website set to custom domain
• Procfile: Web and release process definitions
• scripts/heroku-release.sh: Release phase script for automatic database migrations
• package.json: Pin Node.js version to >= 24.0.0
• .nvmrc: Updated to 24 to match engines field
• HEROKU.md: Deployment documentation with automatic deploy setup and custom domain
• CLAUDE.md: Reference to HEROKU.md for deployment info

Deployment Workflow

Standard Flow (Automatic)

1. Merge PR to main
2. Heroku automatically deploys
3. Release phase runs migrations
4. New dynos start serving traffic

Emergency Flow (Manual)

• git push heroku main --force for break-the-glass situations
• Bypasses automatic deploys, use sparingly

Environment Variables

Variable	Source	Description
DATABASE_URL	Auto-provisioned	PostgreSQL connection
GITHUB_CLIENT_ID	Required	GitHub OAuth
GITHUB_CLIENT_SECRET	Required	GitHub OAuth
BETTER_AUTH_SECRET	Auto-generated	Session encryption
CODEBAR_AUTH_URL	Auto-set	App base URL (auth.codebar.io)

Infrastructure

• Dyno: Basic ($7/month)
• Database: Heroku Postgres Essential-0 ($5/month, 1GB)
• Stack: heroku-24
• Node.js: >= 24.0.0
• Domain: auth.codebar.io

Setup Instructions

See HEROKU.md for:

1. Initial app creation with app.json
2. GitHub repository connection
3. OAuth configuration (using auth.codebar.io)
4. Monitoring commands

Testing

• Create Heroku app from app.json
• Connect GitHub repo for automatic deploys
• Verify migrations run on deploy
• Test GitHub OAuth with auth.codebar.io domain
• Test manual deployment as break-the-glass

[till]

This is good progress.

[mroderick]

Shall we do the cleanups in main first, and then come back to this PR?

[mroderick]

Done! I've pushed follow-up commits that align this PR with the config centralization in main:

1. Changed baseURL to use appConfig.base_url (centralized config)
2. Renamed BETTER_AUTH_URL → CODEBAR_AUTH_URL to match main
3. Fixed minor formatting in HEROKU.md

Ready for review when you are.

[till]

@mroderick feel free to squash, github will show me what is new and auto resolve comments. I'll have a look after.

[mroderick]

Hey @till
I've tidied up this branch since main had a good amount of fixes implemented, so a good amount of the changes here were just noise now.
I've taken your suggestion and split the HEROKU.md into two documents that are not mixing concerns anymore.