### What happened?

On a proxy started **without** a `DATABASE_URL` (a master-key-only deployment, which is a documented, supported configuration), **every** auth failure — including a plain unauthenticated request — returns an unrelated HTTP 500 instead of a 401.

### Root cause

`PrismaDBExceptionHandler.is_database_connection_error` (and its siblings `is_prisma_data_error`, `is_database_transport_error`, `is_prisma_engine_internal_error`) do an unconditional `import prisma` inside the method body.

`prisma` is an *optional* dependency: it's only installed when the proxy is generated/started against a configured `DATABASE_URL` (pulled in by `prisma generate`). A bare master-key-only deployment never installs it.

`is_database_connection_error` is called from `_user_api_key_auth_builder`'s exception handler for **every** auth failure, not just DB-related ones. So on a master-key-only proxy, any request with a missing or wrong API key — including an unauthenticated health check — crashes the classifier itself with `ModuleNotFoundError: No module named 'prisma'`, which surfaces as an HTTP 500 instead of the correct 401.

### Reproduction

Minimal config, no `model_list`, no `databas…