Initial commit: split VNOX monorepo into VNOX-Server

Unified server binary (vnox-serverd) combining:
- Gateway (TCP, auth, channels, sessions, SQLite)
- Voice-node (UDP relay, Opus, jitter buffer)

Standalone gateway (vnox-gateway) and voice-node (vnox-voice-node) preserved as sub-crates.

gateway/src/main.rs

@@ -0,0 +1,12 @@
+use anyhow::Result;
+use std::sync::Arc;
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    tracing_subscriber::fmt()
+        .with_env_filter(std::env::var("VNOX_LOG").unwrap_or_else(|_| "info".into()))
+        .init();
+
+    let cfg = Arc::new(vnox_gateway::domain::config::load()?);
+    vnox_gateway::run(cfg).await
+}