feat: implement staging deployment pipeline with Docker support, auto…

[akinboyewaSamson]

closes #74

Phase 0: Staging Deployment, Rollback, and Smoke Tests
Overview
Implements a multi-stage Docker deployment pipeline with configuration validation, safe database migrations, automated smoke tests, and automatic rollback support to fulfill the "Phase 0" API roadmap requirements.

Changes Made
New Files
Dockerfile - Multi-stage, pnpm-optimized image build process for the API.
.dockerignore - Prevents local artifacts and dependencies from bloating the Docker image.
docker-compose.staging.yml - Orchestration manifest for the staging API and database services.
config/staging.env.example - Explicit staging secrets contract containing required variables.
scripts/deploy-staging.sh - Automates configuration checks, safe Prisma migrations (npx prisma migrate deploy), container deployment, and readiness polling.
scripts/smoke-test.sh - Validates the deployment using the /health endpoint.
scripts/rollback-staging.sh - Automates a safe, migration-forward rollback using previous image digests.
.github/workflows/deploy-staging.yml - CI/CD pipeline combining build, deployment, smoke testing, and conditional rollbacks on failure.
docs/RUNBOOK.md - Technical runbook documenting the deployment strategy, manual execution, and the strict migration-forward schema policy.
Technical Details
Deployment Strategy
Utilizes immutable Docker image tags based on the Git commit SHA (type=sha,format=long).
Database migrations are isolated and applied in an ephemeral container before the application containers are updated to ensure code-schema consistency.
A readiness check continuously polls the /health endpoint for up to 30 seconds before proceeding to smoke tests.
Rollback Strategy (Migration-Forward)
If the deployment or smoke tests fail, the rollback script is automatically invoked.
Rollback intentionally omits database schema downgrades to prevent accidental data loss in staging/production environments.
The system safely reverts only the API container to the previous Docker image digest.
Acceptance Criteria Met
✅ Staging deploys from a known image digest.
✅ Failed readiness or smoke tests stop the promotion and fail the workflow.
✅ Rollback procedure avoids unsafe DB downgrades (migration-forward).
✅ Evidence of deployments, actors, and tests is retained via GitHub Action workflow logs.
✅ The required RUNBOOK.md documentation has been created.

[3m1n3nc3]

Your docker additions are not required for this pr, you should remove them, that should fix the conflicts