chore: remove Docker support entirely from this fork

Never used by this fork's own distribution (install.sh/x-ui.sh is the
only supported install path), AmneziaWG structurally can't run in the
Alpine-based image anyway, and Docker Hub publishing was failing on
every release for lack of configured credentials. Removed Dockerfile,
docker-compose.yml, DockerEntrypoint.sh, DockerInit.sh, .dockerignore,
and the docker.yml CI workflow; dropped the now-dead "Docker" README
subsection (all 7 languages), the "Docker image"/"Docker Compose"
options from the issue/PR templates, and corrected claude-bot.yml's
now-stale references to the deleted files, the never-actually-ours
ghcr.io/mhsanaei/3x-ui image, and (caught in passing) an already-stale
claim that Windows is a supported platform.

Left untouched: generic container-runtime adaptations that apply
regardless of image source (x-ui.sh's running-in-docker detection,
the virtual-interface-name filters, the DNS-over-container-network
note) and deploy/test/smoke-noninteractive.sh, which uses Docker only
as its own test sandbox, not as something this repo ships.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

install.sh

@@ -1565,9 +1565,8 @@ EOF
 # setup_fail2ban auto-installs and configures fail2ban for the IP Limit feature
 # by invoking the freshly installed x-ui CLI. IP Limit is load-bearing on
 # fail2ban (without it the panel disables the limitIp field and zeroes existing
-# limits), so a fresh install should make it work out of the box, just like the
-# Docker image already does. Non-fatal by design: a fail2ban failure must never
-# abort the panel install.
+# limits), so a fresh install should make it work out of the box. Non-fatal by
+# design: a fail2ban failure must never abort the panel install.
 setup_fail2ban() {
     if [[ -n "${XUI_ENABLE_FAIL2BAN+x}" && "${XUI_ENABLE_FAIL2BAN}" != "true" ]]; then
         echo -e "${yellow}XUI_ENABLE_FAIL2BAN=${XUI_ENABLE_FAIL2BAN}, skipping Fail2ban auto-setup.${plain}"