5G Proxy Pro

Locks your phone to the cellular (5G/4G) network and exposes a SOCKS5
proxy server on your local area network (Wi-Fi, hotspot or USB tethering),
so other devices can route their traffic through the phone's cellular
connection.

The proxy engine is a native C implementation (epoll-based) supporting TCP
(CONNECT) and UDP (ASSOCIATE) with IPv4, IPv6 and domain addresses. All
connections are bound to the cellular network via Network.bindSocket().
A heartbeat keeps the cellular link alive, and a health check restarts the
engine automatically if it fails.

Security:
- The listener only binds to LAN interfaces (Wi-Fi / hotspot / USB
tethering); it is never exposed on the cellular interface.
- Optional username/password authentication (RFC 1929): auth is enabled
only when both fields are set. Leave them empty for an open proxy, and
only use it on trusted local networks.
- A foreground service notification shows the proxy status.

Network usage:
- connectivitycheck.gstatic.com/generate_204 - cellular health check
- api.ipify.org - displays the cellular public IP in the app
- Speed test servers (Linode/OVH/Hetzner/Tele2/ThinkBroadband) - only when
using the developer speed test button

A cellular speed test tool is also included.