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/gotify/compose.yml

@@ -1,27 +0,0 @@
-services:
-  gotify:
-    image: gotify/server:latest
-    container_name: gotify
-    restart: unless-stopped
-    ports:
-      - "127.0.0.1:9091:80"
-    volumes:
-      - gotify_data:/app/data
-    environment:
-      - GOTIFY_DEFAULTUSER_NAME=${SECRET:gotify-admin-user}
-      - GOTIFY_DEFAULTUSER_PASS=${SECRET:gotify-admin-pass}
-    networks:
-      - gotify-network
-    healthcheck:
-      test: ["CMD", "wget", "--spider", "-q", "http://localhost:80/health"]
-      interval: 30s
-      timeout: 10s
-      retries: 3
-      start_period: 10s
-
-volumes:
-  gotify_data:
-
-networks:
-  gotify-network:
-    driver: bridge