Embed frontend build output directly into Go binary using //go:embed.
This removes runtime dependency on ../frontend/public/ path and
simplifies Docker builds by serving assets from embedded filesystem.
- Add backend/web/embed.go with embed.FS directive
- Update server to serve from embedded static assets
- Update Makefile to copy frontend build to web/static/
- Update Dockerfile for simplified multi-stage build
- Update frontend package.json output paths
- Remove custom 'oc' command from flake.nix dev shell
Add AETHERA_ prefixed env vars for server configuration:
- AETHERA_DATA_DIR: data directory path
- AETHERA_LISTEN: listen address
- AETHERA_PORT: listen port
Env vars take precedence over defaults but CLI flags override both.
