docs(docker): restore self-hosted PWA compose flow

docker/docker-entrypoint.sh

@@ -0,0 +1,69 @@
+#!/bin/sh
+set -eu
+
+export PORT="${PORT:-3000}"
+export BACKEND_URL="${BACKEND_URL:-/api}"
+
+envsubst '${PORT}' < /etc/nginx/http.d/default.conf.template > /etc/nginx/http.d/default.conf
+
+node <<'NODE'
+const fs = require('node:fs');
+
+fs.writeFileSync(
+    '/usr/share/nginx/html/assets/app-config.js',
+    `window.__IPTVNATOR_CONFIG__ = ${JSON.stringify(
+        { BACKEND_URL: process.env.BACKEND_URL || '/api' },
+        null,
+        2
+    )};\n`
+);
+NODE
+
+node /opt/iptvnator/web-backend/main.cjs &
+BACKEND_PID=$!
+
+cleanup_done=0
+cleanup() {
+    if [ "$cleanup_done" -eq 1 ]; then
+        return
+    fi
+
+    cleanup_done=1
+    trap - INT TERM EXIT
+
+    if [ -n "${NGINX_PID:-}" ]; then
+        kill "$NGINX_PID" 2>/dev/null || true
+    fi
+
+    if [ -n "${BACKEND_PID:-}" ]; then
+        kill "$BACKEND_PID" 2>/dev/null || true
+    fi
+}
+
+trap cleanup INT TERM EXIT
+
+backend_ready=0
+
+for _ in $(seq 1 30); do
+    if wget -qO- "http://127.0.0.1:${PORT}/health" >/dev/null 2>&1; then
+        backend_ready=1
+        break
+    fi
+
+    if ! kill -0 "$BACKEND_PID" 2>/dev/null; then
+        wait "$BACKEND_PID"
+        exit $?
+    fi
+
+    sleep 1
+done
+
+if [ "$backend_ready" -ne 1 ]; then
+    echo "IPTVnator web backend did not become healthy on port ${PORT}."
+    exit 1
+fi
+
+nginx -g 'daemon off;' &
+NGINX_PID=$!
+
+wait "$NGINX_PID"