Merge SERVICE role into AGENT

Every AGENT now gets an auto-generated API key on creation, shown once
in a modal. AGENTs log in with password and authenticate to the API
with X-Api-Key. pre-push.sql defensively migrates any residual SERVICE
rows to AGENT before Prisma rewrites the enum. Goddard is no longer
baked into the seed — create agents via Admin → Users.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

server/prisma/schema.prisma

@@ -11,7 +11,6 @@ enum Role {
   ADMIN
   AGENT
   USER
-  SERVICE
 }
 
 enum TicketStatus {