fix(auth): front CouchDB with nginx to mark AuthSession cookie Secure

CouchDB 3.5 derives the Set-Cookie Secure flag from the raw mochiweb
socket scheme and ignores X-Forwarded-Proto/Ssl for cookie attribution.
Behind a TLS-terminating proxy the cookie was emitted without Secure,
so browsers dropped the SameSite=None AuthSession cookie on cross-origin
requests — POST /_session returned 200 but the next GET /_session showed
userCtx.name: null and PouchDB stayed unauthenticated.

Add an nginx sidecar that adds Secure via proxy_cookie_flags, route the
public domain through it, and make couchdb internal. Also persist
same_site=none in couchdb-init so the setting survives container
recreation (local.d/ is not in the data volume).

README.md

@@ -1,6 +1,14 @@
 # coolcouch
 
-CouchDB 3 on Coolify. The `couchdb-init` sidecar waits for the server to come up, creates the three system databases, and enables CORS via the config API — no file mounts required.
+CouchDB 3 on Coolify, fronted by an nginx sidecar. The `couchdb-init` sidecar waits for the server to come up, creates the three system databases, and applies CORS + cookie config via the config API — no file mounts on CouchDB itself.
+
+## Architecture
+
+```
+client ──https──> Traefik ──http──> nginx ──http──> couchdb (internal)
+```
+
+nginx exists for one reason: to add `Secure` to the `AuthSession` cookie that CouchDB emits. CouchDB only marks cookies `Secure` when its embedded mochiweb sees a true HTTPS socket; behind a TLS-terminating proxy it never does, and it ignores `X-Forwarded-Proto`/`X-Forwarded-Ssl` for cookie attribution. Without `Secure`, browsers reject `SameSite=None` cookies, and cross-origin PouchDB logins silently fail (login returns 200, the next `_session` shows `userCtx.name: null`). The fix is `proxy_cookie_flags AuthSession secure;` in `nginx/default.conf`.
 
 ## Deploy
 
@@ -8,7 +16,8 @@ CouchDB 3 on Coolify. The `couchdb-init` sidecar waits for the server to come up
 2. In the resource's **Environment Variables** tab, set:
    - `COUCHDB_PASSWORD` — required
    - `COUCHDB_USER` — optional, defaults to `admin`
-3. In the resource's **Domains** tab, assign a domain to the `couchdb` service on port `5984`. Coolify fills `SERVICE_FQDN_COUCHDB_5984` from this.
+   - `INVITE_CODE` — required for the signup service
+3. In the resource's **Domains** tab, assign your CouchDB domain to the **`nginx`** service on port `5984` (not `couchdb` directly — that's now internal). Coolify fills `SERVICE_FQDN_NGINX_5984` from this. Assign the signup domain to the `signup` service on port `8080`.
 4. **Deploy.** `couchdb-init` runs once, exits, and won't restart.
 
 ## Verify
@@ -26,6 +35,21 @@ curl -fsS -I -X OPTIONS https://$DOMAIN/ \
 
 Expected: `_up` returns `{"status":"ok",...}`; `/` returns the CouchDB welcome JSON; `_all_dbs` returns `["_global_changes","_replicator","_users"]`; the preflight returns 2xx with an `Access-Control-Allow-Origin` header.
 
+Verify the cookie has both `SameSite=None` and `Secure`:
+
+```bash
+curl -i -X POST https://$DOMAIN/_session \
+  -H 'Content-Type: application/x-www-form-urlencoded' \
+  -d "name=admin&password=$PASS" | grep -i set-cookie
+```
+
+Expected:
+```
+set-cookie: AuthSession=...; Version=1; Expires=...; Max-Age=600; Path=/; HttpOnly; SameSite=None; Secure
+```
+
+If `Secure` is missing, the nginx sidecar isn't fronting the request — check that the Coolify domain is assigned to `nginx:5984` and not to `couchdb` directly.
+
 If the init logs show CORS errors, you can re-trigger only that step by redeploying — the PUTs against `/_node/_local/_config/...` are idempotent.
 
 ## CORS
@@ -87,4 +111,5 @@ The frontend should then `POST https://couch.apoena.dev/_session` with the same
 ## Files
 
 - `docker-compose.yml` — services, volume, Traefik labels, init sidecar
+- `nginx/default.conf` — reverse-proxy config that adds `Secure` to AuthSession cookies
 - `signup/` — Gleam signup service (Dockerfile, gleam.toml, src/)