CI: test against a Postgres service (embedded Postgres won't run as root)

Co-Authored-By: Claude Opus 5.5 <[email protected]>

README.md

@@ -30,4 +30,4 @@ To point a T5DE proxy at it: `t5de-proxy signin -hub http://127.0.0.1:8080`.
 ## Tests
 
 `go test ./...` runs everything, the website and API against a real Postgres (embedded, downloaded on first run
-and cached; `T5DE_PG_CACHE` sets where) and a fake IMVU API.
+and cached; `T5DE_PG_CACHE` sets where), or the Postgres at `T5DE_TEST_DB` (as CI does), and a fake IMVU API.