- payment_handler.py: warn when L402_HMAC_SECRET uses default value
- l402_proxy.py: warn when L402_MACAROON_SECRET uses default value
- .env.example: document L402_HMAC_SECRET, L402_MACAROON_SECRET, and
LIGHTNING_BACKEND with generation instructions
These warnings ensure operators are alerted before deploying with
insecure default secrets.