chore: Update Docker configuration for secure API key management

- Add env_file configuration for Docker

- Remove hardcoded API key references

.env.template

@@ -0,0 +1,5 @@
+# API Keys
+FMP_API_KEY=your_api_key_here
+
+# Cache Configuration
+CACHE_DURATION_HOURS=24

docker-compose.yml

@@ -16,6 +16,8 @@ services:
       - STREAMLIT_SERVER_ENABLE_CORS=true
       - STREAMLIT_SERVER_ENABLE_XSRF_PROTECTION=false
       - STREAMLIT_SERVER_BASE_URL_PATH=
+    env_file:
+      - .env
     restart: unless-stopped
 
   # etf-portfolio: