Add slim docker-compose.dev-remote.yml (app+db+redis, no monitoring)
for the remote dev VPS, and a deploy-dev job that auto-runs after a
successful image build on main. Bump Dockerfile.dev's Rust image so
edition2024 dependencies build. Stop tracking .env.dev (real secrets
were committed) in favor of .env.dev.example / .env.dev-remote.example
templates.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>