fix: enable Rust tracing → Android logcat via tracing-android

Rust tracing subscriber was never initialized — all info!/warn!/error!
calls in the engine went to /dev/null. This meant our send/recv health
logging was invisible and we couldn't confirm the congestion fix was
active.

Now initializes tracing-android layer on first nativeInit(), routing
all Rust logs to logcat under tag "wzp_android". Also expanded logcat
filter in DebugReporter to capture engine-level log lines.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/wzp-android/Cargo.toml

@@ -28,6 +28,7 @@ libc = "0.2"
 jni = { version = "0.21", default-features = false }
 rand = { workspace = true }
 rustls = { version = "0.23", default-features = false, features = ["ring"] }
+tracing-android = "0.2"
 
 [build-dependencies]
 cc = "1"