Dockerfile and docker-compose for API + Postgres + Redis

[tayebmokni]

Summary

Provide multi-stage Dockerfile for the Go API server and a Docker Compose file that brings up the server, Postgres 15, and Redis for local development. This unblocks local testing of every downstream migration / handler issue.

Design reference

• docs/00-architecture-overview.md §2 (Stack Decisions)

Acceptance criteria

• Dockerfile builds a minimal image (distroless or scratch) under 50 MB
• Multi-stage build: deps cache layer, build layer, runtime layer
• docker-compose.yml defines services: api, postgres:15, redis:7
• Compose mounts a named volume for Postgres data
• docker compose up from a fresh clone produces a healthy API responding to /healthz
• Compose includes migrate service or run-once job that applies migrations on boot
• Image runs as non-root user

Dependencies

#2, #5

Complexity

S