feat(net): add UDP server/client with connection management

Adds NetSocket (non-blocking UdpSocket wrapper with local_addr), NetServer
(connection tracking via HashMap, poll/broadcast/send_to_client), and NetClient
(connect/poll/send/disconnect lifecycle). Includes an integration test on
127.0.0.1:0 that validates ClientConnected, Connected, and UserData receipt
end-to-end with 50ms sleeps to ensure UDP packet delivery.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Cargo.lock

@@ -432,6 +432,21 @@ version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f27ae1dd37df86211c42e150270f82743308803d90a6f6e6651cd730d5e1732f"
 
+[[package]]
+name = "deferred_demo"
+version = "0.1.0"
+dependencies = [
+ "bytemuck",
+ "env_logger",
+ "log",
+ "pollster",
+ "voltex_math",
+ "voltex_platform",
+ "voltex_renderer",
+ "wgpu",
+ "winit",
+]
+
 [[package]]
 name = "dispatch"
 version = "0.2.0"
@@ -2029,6 +2044,13 @@ version = "0.9.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0b928f33d975fc6ad9f86c8f283853ad26bdd5b10b7f1542aa2fa15e2289105a"
 
+[[package]]
+name = "voltex_ai"
+version = "0.1.0"
+dependencies = [
+ "voltex_math",
+]
+
 [[package]]
 name = "voltex_asset"
 version = "0.1.0"
@@ -2051,6 +2073,10 @@ dependencies = [
 name = "voltex_math"
 version = "0.1.0"
 
+[[package]]
+name = "voltex_net"
+version = "0.1.0"
+
 [[package]]
 name = "voltex_physics"
 version = "0.1.0"