ci: probe the server's SQL against a Postgres service

Nothing in CI ran a statement against anything but SQLite, so the claim
that the dialect layer keeps the repositories portable was never measured
and new SQLite-only SQL could land unseen. The new postgres-probe job
(server/scripts/pg-probe.ts, npm run probe:pg) does that against a
postgres:17 service container:

- it derives a Postgres schema from the entities with MikroORM's schema
  generator, keeping TEXT timestamps, mapping the SQLite-only defaults and
  the NOCASE collation, and leaving foreign keys out;
- it runs every dialect helper on an in-memory SQLite and on Postgres
  against the same expectation, and every case has to pass;
- it calls every public repository method once with arguments the
  TypeScript checker builds from the parameter types, through a Postgres
  driver that runs each statement alone in a rolled-back transaction with
  a statement timeout and records whether Postgres accepted it.

The statements Postgres refuses are held per method to
scripts/pg-probe-baseline.json, which may only shrink. The baseline starts
unmeasured (failing: null): the job reports, passes and uploads the first
measurement as the pg-probe-baseline artifact, together with a JSON report,
so the commit that seeds it and every later commit that lowers it needs no
local Postgres. The probe refuses a database holding tables it did not
create.

@mikro-orm/postgresql joins the server's devDependencies at the 7.2.1 the
other MikroORM packages resolve to; the image's production install leaves
it out. The job needs the preflight gates like every test job, runs only
for the code area, stops after ten minutes and is part of ci-ok.

server/tsconfig.scripts.json

@@ -4,5 +4,5 @@
     "rootDir": ".",
     "noEmit": true
   },
-  "include": ["scripts/generate-entities.ts", "scripts/generate-db-types.ts", "scripts/migrate-encryption.ts"]
+  "include": ["scripts/generate-entities.ts", "scripts/generate-db-types.ts", "scripts/migrate-encryption.ts", "scripts/pg-probe.ts", "scripts/pg-probe/*.ts"]
 }