fix(presence-service): run prisma generate before nest build

pnpm ignores @prisma/client postinstall scripts in Docker build context,
so generated types are missing. Run prisma generate explicitly as part
of the build script so @prisma/client exports are available to tsc.

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

packages/services/presence-service/package.json

@@ -3,7 +3,7 @@
   "version": "0.1.0",
   "private": true,
   "scripts": {
-    "build": "nest build",
+    "build": "prisma generate && nest build",
     "dev": "nest start --watch",
     "start": "node dist/main",
     "prisma:generate": "prisma generate",