security: sanitize internal infrastructure details from open source package

- Remove production_test_sequence.sh (DAW-specific production tests)
- Remove setup_env.sh (obsolete .env setup, replaced by furt.conf)
- Sanitize test scripts: replace dragons-at-work.de with example.com
- Sanitize API keys: replace dev keys with placeholder values
- Remove hardcoded DAW fallbacks from http_server.lua and smtp.lua
- Update .gitignore to exclude production-specific test files

Tests remain functional for developers with example domains.
All internal DAW infrastructure details removed from package.

Closes #101

scripts/manual_mail_test.sh

@@ -4,11 +4,11 @@
 echo "Testing SMTP with corrected JSON..."
 
 # Simple test without timestamp embedding
-curl -X POST http://127.0.0.1:8080/v1/mail/send \
+curl -X POST http://127.0.0.1:7811/v1/mail/send \
      -H "Content-Type: application/json" \
      -d '{
        "name": "Furt Test User",
-       "email": "michael@dragons-at-work.de",
+       "email": "admin@example.com",
        "subject": "Furt SMTP Test Success!",
        "message": "This is a test email from Furt Lua HTTP-Server. SMTP Integration working!"
      }'