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/vaultwarden-compose.yml

@@ -0,0 +1,28 @@
+services:
+  vaultwarden:
+    image: vaultwarden/server:latest
+    container_name: vaultwarden
+    restart: unless-stopped
+    ports:
+      - "127.0.0.1:8080:80"
+    volumes:
+      - vaultwarden_data:/data
+    environment:
+      - ADMIN_TOKEN=${SECRET:vaultwarden-admin-token}
+      - WEBSOCKET_ENABLED=true
+      - SIGNUPS_ALLOWED=false
+    networks:
+      - vaultwarden-network
+    healthcheck:
+      test: ["CMD", "wget", "--spider", "-q", "http://localhost:80/alive"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+      start_period: 10s
+
+volumes:
+  vaultwarden_data:
+
+networks:
+  vaultwarden-network:
+    driver: bridge