fix: prevent restart loop on missing API keys

Add validation at startup to check required environment variables:
- OPENAI_API_KEY
- ALPHAADVANTAGE_API_KEY
- JINA_API_KEY

If any are missing, display clear error message with setup
instructions and exit immediately (no restart loop).

Change restart policy from 'unless-stopped' to 'on-failure:3'
to limit restart attempts and prevent endless loops on
configuration errors.

docker-compose.yml

@@ -34,4 +34,4 @@ services:
       - "${TRADE_HTTP_PORT:-8002}:8002"
       - "${GETPRICE_HTTP_PORT:-8003}:8003"
       - "${WEB_HTTP_PORT:-8888}:8888"
-    restart: unless-stopped
+    restart: on-failure:3  # Restart max 3 times on failure, prevents endless loops