feat: Flatten stack structure - all stacks directly in stacks/

- Removed all subdirectories
- Renamed compose.yml to <stack>-compose.yml
- Updated stack.toml to reference new compose file names
- Structure is now flat for easier Komodo sync

New structure:
stacks/
├── prometheus.toml
├── prometheus-compose.yml
├── grafana.toml
├── grafana-compose.yml
├── gotify.toml
├── gotify-compose.yml
├── vaultwarden.toml
├── vaultwarden-compose.yml
└── node-exporter.toml
└── node-exporter-compose.yml

stacks/grafana-compose.yml

@@ -0,0 +1,30 @@
+services:
+  grafana:
+    image: grafana/grafana:latest
+    container_name: grafana
+    restart: unless-stopped
+    ports:
+      - "127.0.0.1:3000:3000"
+    volumes:
+      - grafana_data:/var/lib/grafana
+      - grafana_config:/etc/grafana
+    environment:
+      - GF_SECURITY_ADMIN_USER=${SECRET:grafana-admin-user}
+      - GF_SECURITY_ADMIN_PASSWORD=${SECRET:grafana-admin-pass}
+      - GF_USERS_ALLOW_SIGN_UP=false
+    networks:
+      - monitoring
+    healthcheck:
+      test: ["CMD-SHELL", "wget --spider -q http://localhost:3000/api/health || exit 1"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+      start_period: 30s
+
+volumes:
+  grafana_data:
+  grafana_config:
+
+networks:
+  monitoring:
+    driver: bridge