Containerize scraper and externalize credentials

Move DB host/user/password, Discord webhook, and log path to env vars
so the script can be deployed via Docker compose. Discord notifications
are now skipped silently when DISCORD_WEBHOOK is unset (the old
hardcoded webhook is removed pending rotation). Adds Dockerfile,
docker-compose.yml, requirements.txt, .env.example, and .gitignore for
the cyrion deployment.

.gitignore

@@ -0,0 +1,7 @@
+.env
+__pycache__/
+*.pyc
+.venv/
+venv/
+historical_data/
+*.log