mkcert Web UI 4.3.4

Fixed

• UI-saved settings lost on container recreation (#45). The sample
  docker-compose.yml persisted /app/certificates, /app/data, and the
  mkcert root CA, but not /app/config — where settings saved from the web
  UI (config/settings.json: webhook, email/ntfy notifications, theme, ...)
  are stored. Pulling a new image therefore wiped them. The compose file now
  mounts a mkcert_config volume at /app/config, and the manual
  docker run example in docs/DOCKER.md includes the config and CA
  volumes.

  Upgrading an existing deployment: add the volume to your compose file
  before recreating the container —

  services:
    mkcert-web-ui:
      volumes:
        - mkcert_config:/app/config
  volumes:
    mkcert_config:
      driver: local

Documentation

• Documented the certificate-expiry notification environment variables
  (WEBHOOK_ENABLED, WEBHOOK_URL, NTFY_*, EMAIL_NOTIFICATIONS_ENABLED,
  CERT_MONITORING_*) in the sample docker-compose.yml and
  docs/DOCKER.md — they existed but were not documented anywhere (#45).
• Corrected docs/SETTINGS.md, which still described the pre-4.0.0
  precedence order: explicitly-set environment variables override
  config/settings.json, not the other way around.
• Fixed the theme variable name in docs/DOCKER.md (THEME_MODE, not
  DEFAULT_THEME).

Full Changelog: v4.3.3...v4.3.4