## Context

The current `docker-compose.yml` is a standalone development setup without reverse proxy support. The API has hardcoded Authentik URLs in `config.py` (`https://authentik.local/...`) which makes it impossible to deploy in real environments without code changes. The frontend also hardcodes `VITE_API_URL=http://localhost:8000`.

For production deployment, the platform needs to work behind an existing Traefik reverse proxy (common in self-hosted stacks) and have all external service endpoints fully configurable.

## Goals / Non-Goals

**Goals:**
- Make all Authentik URLs configurable via environment variables (no hardcoded defaults).
- Make OAuth redirect/callback URLs configurable and domain-aware.
- Create `docker-compose.traefik.yml` for deployment behind an existing Traefik instance.
- Support configuring the public web domain, API domain, and Authentik domain via env vars.
- Ensure both development (`docker-compose.yml`) and traefik modes work correctly.

**Non-Goals:**
- Setting up Traefik itself (assumes existing Traefik instance).
- Authentik installation/configuration (assumes existing Authentik instance).
- SSL certificate management (handled by Traefik).
- Changing the authentication flow or token logic.

## Decisions

1. **Remove all hardcoded URLs from `config.py` and require env vars**
   - Rationale: Deployment environments have different domains. Hardcoded values are a deployment blocker.
   - Alternative: Keep defaults and override in prod. Rejected because defaults mask configuration errors.

2. **Use `API_DOMAIN` and `WEB_DOMAIN` env vars for constructing public URLs**
   - Rationale: Centralizes domain configuration and makes it easy to switch between dev/prod.
   - `API_PUBLIC_URL` will default to `http://${API_DOMAIN}` or can be overridden.
   - `WEB_PUBLIC_URL` will default to `http://${WEB_DOMAIN}` or can be overridden.

3. **Create a separate `docker-compose.traefik.yml` instead of modifying the existing one**
   - Rationale: The existing `docker-compose.yml` is for standalone development. Traefik deployment is a different topology.
   - Alternative: Use compose profiles or overrides. Rejected to keep each file simple and explicit.

4. **Add `VITE_APP_URL` for the frontend so it knows its public URL**
   - Rationale: OAuth redirect URI needs to be absolute and must match the public web URL.
   - Frontend will use this for login redirect if needed.

5. **Use Traefik labels for routing instead of ports**
   - Rationale: Standard Traefik pattern - services are discovered via Docker labels.
   - No port mappings exposed; Traefik handles all ingress.

## Risks / Trade-offs

- **[Missing env vars cause startup failures]** -> Document all required variables in `.env.example` and add validation in config.py.
- **[OAuth redirect URI mismatch]** -> Ensure the redirect URI configured in Authentik matches the env-configured callback URL exactly.
- **[Local development still works]** -> Keep `docker-compose.yml` unchanged for dev; traefik file is additive.
- **[Cookie secure flag]** -> Ensure `cookie_secure` property in config reads from env properly for HTTPS deployments.

## Migration Plan

1. Update `config.py` to read all Authentik URLs from environment with no defaults.
2. Update `auth.py` to construct redirect/callback URLs from env-configured domains.
3. Update `.env.example` with all new variables.
4. Create `docker-compose.traefik.yml` with Traefik labels.
5. Test that both `docker-compose.yml` (dev) and `docker-compose.traefik.yml` (prod) work.

Rollback:
- Revert config.py and auth.py changes; remove `docker-compose.traefik.yml`.

## Open Questions

- Should we add a startup health check that validates all required env vars are set?