Add Docker + nginx deployment for homelab

- Multi-stage Dockerfile: Node builds static assets, nginx serves them
- nginx proxies /api/* to football-data.org and injects X-Auth-Token
  server-side via FOOTBALL_API_KEY env var (key never in browser bundle)
- docker-compose.yml exposes the app on port 3000
- Extract apiFetch() helper: sends key in dev (Vite proxy), skips in prod
- .env.example updated with both dev and production key vars

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -0,0 +1,8 @@
+services:
+  football-app:
+    build: .
+    restart: unless-stopped
+    ports:
+      - "3000:80"
+    environment:
+      - FOOTBALL_API_KEY=${FOOTBALL_API_KEY}