debug(passenger-api): expose Prisma error code in 500 response body

Adds prismaCode and prismaMeta fields to 500 responses so the exact
Prisma error code (P2022, P2023, etc.) is visible in curl/Swagger without
needing server log access. Temporary diagnostic aid.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/edr-passenger-api/src/common/filters/http-exception.filter.ts

@@ -24,7 +24,11 @@ export class HttpExceptionFilter implements ExceptionFilter {
     const request = ctx.getRequest();
 
     let prismaMessage: string | null = null;
+    let prismaCode: string | null = null;
+    let prismaMeta: unknown = null;
     if (exception instanceof PrismaClientKnownRequestError) {
+      prismaCode = exception.code;
+      prismaMeta = exception.meta;
       if (exception.code === 'P2003') {
         const field = (exception.meta?.field_name as string | undefined) ?? 'a related record';
         prismaMessage = `Cannot delete this record because it is still referenced by ${field}. Remove the related records first.`;
@@ -68,6 +72,7 @@ export class HttpExceptionFilter implements ExceptionFilter {
       statusCode: status,
       message,
       error: exception instanceof Error ? exception.name : 'Error',
+      ...(prismaCode ? { prismaCode, prismaMeta } : {}),
       timestamp: new Date().toISOString(),
       path: request.url,
       ...customFields,