fix: set explicit prisma client output for pnpm compatibility

pnpm's strict node_modules layout causes prisma generate to output to
a deeply nested .pnpm directory, but @prisma/client resolves .prisma/client
from the root node_modules. Setting an explicit output path ensures the
generated client is always found at the expected location.

packages/prisma/schema.prisma

@@ -4,6 +4,7 @@ generator kysely {
 
 generator client {
   provider = "prisma-client-js"
+  output   = "../../node_modules/.prisma/client"
 }
 
 generator json {