feat: migrate to sing-box v1.13+ native DNS config

- Replace deprecated dns.servers[] with new format (type + server + server_port)
- Add _make_dns_server() to parse udp://, tls://, https:// and bare IP addresses
- Drop ENABLE_DEPRECATED_* environment variable shims — fully v1.14-ready
- Fix transport block: omit for plain TCP (sing-box default), add httpupgrade support
- Add dns.final fallback and route.default_domain_resolver
- Config file renamed to hidden /tmp/.sub2socks.json (matches README)
- Include test_proxy.py live proxy CONNECT test suite

test_proxy.py

@@ -0,0 +1,71 @@
+#!/usr/bin/env python3
+"""Comprehensive SOCKS5 proxy test — run inside sub2socks container."""
+import socket
+import struct
+import time
+
+print("=" * 60)
+print("  Sub2SOCKS Live Proxy Test Suite")
+print("=" * 60)
+
+# Test 1: SOCKS5 handshake
+print("\n[1] SOCKS5 Handshake")
+try:
+    s = socket.create_connection(("127.0.0.1", 2080), timeout=15)
+    s.sendall(b"\x05\x01\x00")
+    resp = s.recv(2)
+    ok = (resp == b"\x05\x00")
+    print(f"    Response: {resp.hex():>6}  -> {'PASS' if ok else 'FAIL'}")
+except Exception as e:
+    print(f"    ERROR: {e}")
+    ok = None
+
+# Test 2: CONNECT requests
+print("\n[2] SOCKS5 CONNECT Targets")
+targets = [
+    ("api.ipify.org", 443, "ipify API"),
+    ("httpbin.org",   443, "httpbin      "),
+    ("google.com",     80, "Google HTTP  "),
+    ("cloudflare.com", 443, "Cloudflare   "),
+]
+
+for host, port, label in targets:
+    try:
+        s2 = socket.create_connection(("127.0.0.1", 2080), timeout=20)
+        s2.sendall(b"\x05\x01\x00")
+        s2.recv(2)
+
+        hbytes = host.encode()
+        req = (b"\x05\x01\x00\x03"
+               + bytes([len(hbytes)])
+               + hbytes
+               + struct.pack("!H", port))
+
+        t0 = time.monotonic()
+        s2.sendall(req)
+        conn_resp = s2.recv(8)
+        elapsed = (time.monotonic() - t0) * 1000
+        status_byte = conn_resp[1]
+        if status_byte == 0:
+            print(f"    {label:13s} :{port:<4}  SUCCESS  ({elapsed:.0f} ms)")
+        else:
+            print(f"    {label:13s} :{port:<4}  FAIL (code={status_byte})")
+        s2.close()
+    except socket.timeout:
+        print(f"    {label:13s} :{port:<4}  TIMEOUT")
+    except Exception as e:
+        print(f"    {label:13s} :{port:<4}  ERROR: {e}")
+
+# Test 3: Process health
+print("\n[3] Process health")
+try:
+    with open("/proc/1/cmdline", "rb") as f:
+        cmdline = f.read().decode("utf-8", errors="replace").replace("\x00", " ")
+    has_sb = "sing-box" in cmdline
+    print(f"    PID 1: {'sing-box OK' if has_sb else cmdline[:80]}")
+except Exception as e:
+    print(f"    ERROR reading /proc/1: {e}")
+
+print("\n" + "=" * 60)
+print("  Tests complete")
+print("=" * 60)