Hiddify subscription proxy

Endpoints:
  GET /healthz
  GET /sub/{SUBSCRIPTION_TOKEN}
  GET /sub/{SUBSCRIPTION_TOKEN}.txt
  GET /sub/{SUBSCRIPTION_TOKEN}.yaml
  GET /import?token={SUBSCRIPTION_TOKEN}

Configure:
  UPSTREAM_URL          upstream URL prefix or template with {token}
  UPSTREAM_USER_AGENT   upstream fetch UA, default HiddifyNext/4.0.0
  OUTPUT_FORMAT         auto, clash/raw, or uri; default auto
  PUBLIC_BASE_URL       public base URL used by /import

Import into Hiddify:
  Use /sub/{SUBSCRIPTION_TOKEN}.txt for Hiddify 4.x.