Fix Prisma engine load on Alpine: install openssl + pin musl-openssl-3.0.x

node:20-alpine ships OpenSSL 3.x and has no libssl.so.1.1. Without the
openssl CLI, Prisma's version detection failed and fell back to the
openssl-1.1.x engine, which then failed to load its shared library and
emitted plain text instead of JSON ("Unexpected token 'E'..."), crashing
`prisma migrate deploy` at container startup.

- Install openssl in the build and runtime stages so detection succeeds
- Pin binaryTargets to linux-musl-openssl-3.0.x so the correct engine is bundled

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/prisma/schema.prisma

@@ -1,5 +1,6 @@
 generator client {
-  provider = "prisma-client-js"
+  provider      = "prisma-client-js"
+  binaryTargets = ["native", "linux-musl-openssl-3.0.x"]
 }
 
 datasource db {