fix(playground): increase engine memory limit 3584M→5120M to prevent OOM kills (#221)

Engine uses ~3.6 GB idle with GLiNER+embedding models loaded, causing 10+ OOM kills
today (DAK-6925). Server already hotfixed to 5120M; this syncs the deploy repo.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: ferhimedamine

docker/docker-compose.playground.yml

@@ -2,7 +2,7 @@
 # Dakera Playground — Resource-Limited Single-Node Stack (DAK-6706)
 # =============================================================================
 # Playground limits vs production:
-#   Dakera:  3.5 GB RAM / 3 vCPU (vs 8 GB / 4 vCPU)
+#   Dakera:  5 GB RAM / 3 vCPU (vs 8 GB / 4 vCPU)
 #   MinIO:   1.5 GB RAM / 1 vCPU (vs 4 GB / 2 vCPU)
 #   Body:    5 MB max (vs 500 MB)
 #   Timeout: 30 s (vs 600 s)
@@ -50,7 +50,7 @@ services:
     deploy:
       resources:
         limits:
-          memory: 3584M
+          memory: 5120M
           cpus: "3.0"
         reservations:
           memory: 512M