feat: add PR preview environment workflow

[solarhell]

Summary

• Add GitHub Actions workflow for automatic PR preview deployments
• Each PR gets an isolated Dory instance at pr-<number>.preview.getdory.dev
• Uses Traefik + Docker on a self-hosted VPS with auto SSL via Let's Encrypt

How It Works

1. PR opened/updated → build Docker image → push to DockerHub → deploy to VPS
2. Traefik auto-discovers containers via Docker labels → provisions SSL certificate
3. PR closed → container and image automatically cleaned up

PR Comment Lifecycle

A single bot comment tracks the deployment status through its lifecycle:

Status	When
🔨 Building	Image build started
✅ Ready	Deployment successful, preview URL is live
⏳ Queued	Preview slots full (max 3 concurrent)
❌ Failed	Deployment failed (with link to workflow logs)
🗑️ Destroyed	PR closed, environment cleaned up

Required Secrets

Secret	Description
PREVIEW_SERVER_HOST	VPS IP address
PREVIEW_SERVER_USER	SSH user (root)
PREVIEW_SERVER_SSH_KEY	SSH private key
PREVIEW_AUTH_SECRET	Better Auth secret for preview instances

DOCKERHUB_USERNAME and DOCKERHUB_TOKEN should already be configured.

Infrastructure

Server provisioning is managed in dorylab/infra (Ansible + Traefik).

Closes #134

[vercel]

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Project	Deployment	Actions	Updated (UTC)
dory	Ready	Preview, Comment	Apr 1, 2026 7:36am

2 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
dory-admin	Ignored		Apr 1, 2026 7:36am
dory-beta	Ignored		Apr 1, 2026 7:36am

[github-actions]

Preview Environment for this PR

Name	Status	Preview	Updated (UTC)
pr-136	❌ Failed (cb4a8a5)	—	2026-04-01 07:29:51

Deployment failed. Check the workflow logs for details.