feat: enable udpgw via tun2proxy CLI API — no fork needed (#271)

Uses tun2proxy_run_with_cli_args (the C API) via dlsym instead of
modifying the JNI run() signature. The upstream tun2proxy maintainer
recommended this path — the CLI API accepts --udpgw-server natively.

- Cargo.toml: enable udpgw feature, remove [patch.crates-io]
- MhrvVpnService.kt: build CLI args with --udpgw-server in full mode
- Native.kt + android_jni.rs: dlsym wrapper for the C API
- Tun2proxy.kt: reverted to upstream signature

No fork, no patch, no submodule.

Co-authored-by: yyoyoian-pixel <279225925+yyoyoian-pixel@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Cargo.toml

@@ -100,12 +100,6 @@ tun2proxy = { version = "0.7", default-features = false, features = ["udpgw"] }
 # Used in mitm tests to sanity-check the cert extensions we emit.
 x509-parser = "0.16"
 
-# Temporary patch: adds udpgw_server parameter to the Android JNI run()
-# function. Upstream PR: https://github.com/tun2proxy/tun2proxy/pull/247
-# Remove this section once tun2proxy >= 0.8 ships with the change.
-[patch.crates-io]
-tun2proxy = { git = "https://github.com/yyoyoian-pixel/tun2proxy", branch = "feat/udpgw-jni-param" }
-
 [profile.release]
 panic = "abort"
 codegen-units = 1