fix: sync production DB schema for task detail API

Always run prisma db push on Render build and start so milestones/files columns exist for GET /tasks/:id.

render.yaml

@@ -3,8 +3,8 @@ services:
     name: eene-dashboard-backend
     runtime: node
     rootDir: backend
-    buildCommand: npm install --include=dev && npx prisma migrate deploy || npx prisma db push && npx prisma generate && npm run build
-    startCommand: npm start
+    buildCommand: npm install --include=dev && (npx prisma migrate deploy || true) && npx prisma db push && npx prisma generate && npm run build
+    startCommand: npx prisma db push && npm start
     envVars:
       - key: DATABASE_URL
         sync: false   # Render 대시보드에서 직접 입력