Retry PostgreSQL queries without statement_timeout behind PgBouncer - #1323

Summary

A PostgreSQL DATABASE connector behind PgBouncer fails on every query. executePostgres passes statement_timeout in the Pool config, node-postgres sends it as a startup parameter, and PgBouncer answers unsupported startup parameter: statement_timeout (SQLSTATE 08P01). The connection test passes, because it does not set the timeout. Reported in #1296 after the multi-connector fix made that connector reachable.

Changes

• database.engine.ts: executePostgres still sets statement_timeout (60 s) on the server first. When the error says unsupported startup parameter, it retries once with node-postgres' client-side query_timeout (same 60 s) instead. Any other error is thrown as before.
• The query itself moved into runPostgres, unchanged.
• No SET statement_timeout after connecting: with PgBouncer in transaction mode the setting would stay on the server connection and reach other clients.
• Same behaviour on Cloud and self-hosted. Without PgBouncer nothing changes.

Type

• Bug fix
• New feature
• Documentation
• Refactoring
• Performance improvement
• Other (describe below)

Testing

• Added/updated unit tests
• Tested manually (describe steps below)
• No tests needed (explain why)

Three new tests in database.engine.spec.ts: server timeout by default, retry with query_timeout (and no statement_timeout) on the PgBouncer error, no retry on other errors.

In packages/backend, after npx prisma generate:

• npm run lint: OK (no unrelated rewrites).
• npx tsc --noEmit -p tsconfig.json: OK.
• npm test: 800 suites passed, 4 skipped; 23,694 tests passed, 1,625 skipped.

Checklist

• My code follows the existing code style
• I have tested my changes locally
• I have updated documentation (if applicable)
• All existing tests pass (npm test)
• This PR has a descriptive title

Related Issues

Relates to #1296.