Add Docker self-hosting and CI/CD pipeline

- Dockerfile: Caddy + PHP-FPM + app in single Alpine container
- Caddyfile: auto-HTTPS, security headers, short URL rewrite
- docker-compose.yml: app + Watchtower for auto-updates
- install.sh: one-liner for fresh VPS setup
- GitHub Actions: build & push to Docker Hub + GHCR on tag

Self-host with:
  curl -sL https://xmrpay.link/install.sh | sh -s your-domain.com

install.sh

@@ -0,0 +1,60 @@
+#!/bin/sh
+set -e
+
+# xmrpay.link — Self-hosting installer
+# Usage: curl -sL https://xmrpay.link/install.sh | sh -s your-domain.com
+
+DOMAIN="${1:-}"
+INSTALL_DIR="/opt/xmrpay"
+IMAGE="schmidt1024/xmrpay:latest"
+COMPOSE_URL="https://raw.githubusercontent.com/schmidt1024/xmrpay.link/master/docker-compose.yml"
+
+# ── Helpers ───────────────────────────────────────────────────────────────────
+
+info()  { printf '\033[1;34m→\033[0m %s\n' "$1"; }
+ok()    { printf '\033[1;32m✓\033[0m %s\n' "$1"; }
+fail()  { printf '\033[1;31m✗\033[0m %s\n' "$1" >&2; exit 1; }
+
+# ── Preflight ─────────────────────────────────────────────────────────────────
+
+[ "$(id -u)" -eq 0 ] || fail "Run as root: curl -sL https://xmrpay.link/install.sh | sudo sh -s $DOMAIN"
+[ -n "$DOMAIN" ]      || fail "Usage: curl -sL https://xmrpay.link/install.sh | sh -s YOUR-DOMAIN.COM"
+
+# ── Install Docker if missing ─────────────────────────────────────────────────
+
+if ! command -v docker >/dev/null 2>&1; then
+  info "Installing Docker..."
+  curl -fsSL https://get.docker.com | sh
+  systemctl enable --now docker
+  ok "Docker installed"
+else
+  ok "Docker found"
+fi
+
+# ── Set up xmrpay ────────────────────────────────────────────────────────────
+
+info "Setting up xmrpay in $INSTALL_DIR..."
+mkdir -p "$INSTALL_DIR"
+cd "$INSTALL_DIR"
+
+curl -fsSL "$COMPOSE_URL" -o docker-compose.yml
+
+cat > .env <<EOF
+DOMAIN=$DOMAIN
+XMRPAY_IMAGE=$IMAGE
+EOF
+
+# ── Start ─────────────────────────────────────────────────────────────────────
+
+info "Starting xmrpay..."
+docker compose pull
+docker compose up -d
+
+ok "xmrpay is running!"
+echo ""
+echo "  https://$DOMAIN"
+echo ""
+echo "  Watchtower checks for updates every 6 hours."
+echo "  Data stored in Docker volume: xmrpay-data"
+echo "  Config: $INSTALL_DIR/.env"
+echo ""