Add postgres service (todo §3); pin postgres:18.4-alpine3.23, one DB per Kratos/Keto/Hydra via init.sql

todo.md

@@ -57,7 +57,7 @@ everything via Docker.
 - [x] Go over all tests and combine/unify ones that cover the same stuff or are very related and could be combined in a good way. Remove tests that aren't helping, we only want tests that are actually helpful to us. → Reviewed all 24 test files. The suite already follows the deliberate per-module "matrix + edge" pattern from the §0/§1 merge (line 22), so most files carry no fat and force-merging distinct concerns would only hurt readability. Removed the genuine §2-era overlaps, all in `app.test.ts`: merged the two HTTP static tests into one (GET/HEAD + traversal/NUL→403), and dropped the standalone "renders the 403 error page" `ejs.renderFile` stopgap (its comment even said "403 has no first-party route yet") — the gated plugin route now exercises 403 over HTTP, so the template assertions (status + 403.ejs body + stylesheet link) moved there; also dropped the now-unused `ejs` import. Unified `view-resolver.test.ts`'s two `resolveViewPath` cases (resolve + reject) into one. 113 → 110 tests, zero coverage lost; typecheck + tests green.
 
 ## 3. Ory stack — compose + config
-- [ ] `postgres` service (pinned tag); separate DB/schema per Kratos/Keto/Hydra.
+- [x] `postgres` service (pinned tag); separate DB/schema per Kratos/Keto/Hydra. → `compose.yml` `postgres` service pinned to `postgres:18.4-alpine3.23` (verified latest stable PG + newest Alpine the official image ships); `ory/postgres/init/init.sql` (mounted at `docker-entrypoint-initdb.d`) creates one DB per service (`kratos`/`keto`/`hydra`) so each owns its schema + migrations. Dev defaults (`ory`/`ory`, env-overridable for prod), named `pgdata` volume mounted at `/var/lib/postgresql` (PG18+ version-subdir layout — not `/data`), `pg_isready` healthcheck. Web app never connects. Verified live: boots healthy, three DBs present, then torn down. `postgres.test.ts` guards the pin + DB-per-service. typecheck + 112 units green.
 - [ ] `kratos` service (pinned) + `migrate`; identity schema (traits: email, name).
 - [ ] Kratos self-service flows (login, registration, recovery, verification, settings) → return URLs at our themed pages.
 - [ ] Kratos OIDC/SSO providers (Google/Microsoft/SAML) config (secrets via env). **None enabled by default** — a clean clone runs password-only; a provider activates purely by supplying its env creds.