feat: Restructure to subdirectories with compose.yml

Each stack now has its own directory with standard compose.yml:
- stacks/gotify/compose.yml
- stacks/prometheus/compose.yml
- stacks/grafana/compose.yml
- stacks/vaultwarden/compose.yml
- stacks/node-exporter/compose.yml

Benefits:
- Cleaner structure
- Easier to maintain
- Works with Komodo manual stack creation
- README.md for each stack with deployment info

Usage in Komodo:
1. Stacks → Add Stack
2. Source: Git Repo (nocci/komodo-stacks)
3. Path: stacks/<stack-name>/ (the folder!)
4. Deploy to server

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