feat(xtream-proxy): rewrite proxy logic and update configuration format

Refactor the xtream-proxy from a single-file Express-based server to a
modular Node.js application using native http/https modules. This
change introduces a major version bump to 2.0.0.

- Replace `hosts.txt` with `upstreams.json` for configuration
- Remove heavy dependencies (`express`, `ws`) in favor of native modules
- Implement new environment variables for proxy credentials and timeouts
- Add `src/` directory for modular code structure
- Add `docker-compose.example.yml` for easier deployment
- Update Dockerfile to support the new directory structure and environment
- Improve error handling and probe logic for upstream selection

Dockers/xtream-proxy/docker-compose.example.yml

@@ -0,0 +1,17 @@
+services:
+  xtream-proxy:
+    build: .
+    container_name: xtream-proxy
+    ports:
+      - "8080:8080"
+    environment:
+      PROXY_USERNAME: "${PROXY_USERNAME}"
+      PROXY_PASSWORD: "${PROXY_PASSWORD}"
+      PROBE_INTERVAL_SEC: "30"
+      PROBE_TIMEOUT_MS: "8000"
+      UPSTREAM_TIMEOUT_MS: "15000"
+      ALLOW_BUSY_FALLBACK: "1"
+      # PROXY_INSECURE_TLS: "1"   # alleen nodig bij self-signed upstream-certificaten
+    volumes:
+      - ./upstreams.json:/config/upstreams.json:ro
+    restart: unless-stopped