feat: add CI/CD pipeline, production Dockerfile, and deployment architecture

- Add production Dockerfile with bun build --compile, multi-stage Alpine build
- Add .dockerignore
- Swap bcrypt -> bcryptjs (pure JS, no native addons)
- Add programmatic migrations on startup via drizzle migrator
- Add /v1/version endpoint with APP_VERSION baked in at build time
- Add .gitea/workflows/ci.yml (lint + test with postgres/valkey services)
- Add .gitea/workflows/build.yml (version bump, build, push to registry)
- Update CLAUDE.md and docs/architecture.md to remove multi-tenancy
- Add docs/deployment.md covering DOKS + ArgoCD architecture

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.dockerignore

@@ -0,0 +1,11 @@
+node_modules
+.git
+.gitea
+docs
+planning
+deploy
+infra
+packages/admin
+Dockerfile*
+docker-compose*
+*.md