fix(cli): add hardcoded fallback for service required parameters

[dviejokfs]

Summary

• Fixed service creation still failing after PR fix(cli): populate required parameters when creating services in wizard #7 because the schema API call (GET /external-services/types/{type}/parameters) returns { error } without throwing, causing requiredFields to stay empty
• Added KNOWN_REQUIRED_FIELDS hardcoded fallback map so PostgreSQL and MongoDB always get database and username populated regardless of whether the schema fetch succeeds

Root cause

The @hey-api client doesn't throw on HTTP errors — it returns { data: undefined, error: ... }. The previous try/catch only caught network-level exceptions, not API-level errors. When the schema call returned an error response, requiredFields stayed [] and no parameters were generated.

Fix

Two-layer approach:

1. Check error from the API response (not just rely on try/catch)
2. Hardcoded fallback: if schema fetch returns nothing, use KNOWN_REQUIRED_FIELDS[serviceType] which maps postgres → ['database', 'username'] and mongodb → ['database', 'username']

This ensures service creation works even if the schema endpoint is unreachable, returns an error, or changes format.