style(portal-bff): apply prettier to check-database-url.ts (#71)

## Summary

Cosmetic-only follow-up to #70. Collapses one over-cautious multi-line `throw new Error(...)` into a single line that fits within the project's 100-char `printWidth`.

The reformat was produced by lint-staged **during** the amend that landed #70, but applied to the working tree only — the modification never made it back into the staged content of the amend. The merged commit therefore carries the un-prettified version.

Spotted locally with `pnpm exec prettier --check apps/portal-bff/src/config/check-database-url.ts` failing. Left unchecked, the next PR's `check` job would break at `format:check` for unrelated reasons.

## Test plan

- [ ] CI green on this PR (`format:check` clean).
- [ ] No behavioural change — only whitespace.

---------

Co-authored-by: Julien Gautier <julien.gautier@apf.asso.fr>
Reviewed-on: #71

apps/portal-bff/src/config/check-database-url.ts

@@ -34,9 +34,7 @@ export function assertDatabaseUrl(): void {
   }
 
   if (parsed.protocol !== 'postgresql:' && parsed.protocol !== 'postgres:') {
-    throw new Error(
+    throw new Error(`DATABASE_URL must use the "postgresql://" scheme; got "${parsed.protocol}".`);
-      `DATABASE_URL must use the "postgresql://" scheme; got "${parsed.protocol}".`,
-    );
   }
 
   // Heuristic — multiple "@" before the path almost always means the