Add CAP_KILL capability and remove stop_grace_period

- Add KILL to cap_add for graceful shutdown with init systems (s6/s6-overlay)
- Remove stop_grace_period (no longer needed with CAP_KILL)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

docker-compose.yaml

@@ -10,10 +10,11 @@ services:
     cap_drop:
       - ALL
     cap_add:
-      - CHOWN           # Config file ownership
-      - SETUID          # User switching in entrypoint
-      - SETGID          # Group switching in entrypoint
-      - DAC_OVERRIDE    # Permission override for config files
+      - KILL
+      - CHOWN
+      - SETUID
+      - SETGID
+      - DAC_OVERRIDE
 
     # Resource Limits
     deploy:
@@ -26,8 +27,6 @@ services:
           memory: 256M
           cpus: '0.25'
 
-    stop_grace_period: 15s
-
     # macvlan Network - HomeKit mDNS Discovery
     networks:
       docker_macvlan: