* chore(deploy): trust proxy headers + document HTTPS env vars
- uvicorn: add --proxy-headers --forwarded-allow-ips='*' so the app honors
X-Forwarded-Proto/Host from a TLS-terminating reverse proxy (Caddy,
Cloudflare Tunnel, nginx, LB). Without this the app saw every request as
plain HTTP and built redirect/OAuth URLs from the raw Host, which is
fragile behind a proxy.
- .env.template: document DOMAIN (enables Secure cookie flag) and new
SERVER_URL (deterministic base URL for OAuth callbacks and external
links). Grouped under a dedicated HTTPS / REVERSE PROXY section.
* chore(deploy): add proxy header flags to Dockerfile CMD and Kamal config
Matches the docker-compose changes so non-compose deployments (docker run,
Kubernetes, ECS, Kamal) also trust X-Forwarded-Proto/X-Forwarded-For.
* fix(auth): align Google OAuth cookie Secure flag with password/email providers
Google OAuth set the access_token cookie Secure flag based on the TESTING env
var, while password and email providers use DOMAIN. This meant the DOMAIN
env var (now documented in config/.env.template) did not actually control
Secure for Google cookies. Align all three providers on DOMAIN so the
documented behavior holds consistently.
