feat: add mesh network visualizer

- D3.js force-directed graph for real-time mesh visualization
- WebSocket server (mesh-viz-bridge crate) for live updates
- Demo mode with simulated topology
- JSONL file upload for offline analysis
- Optional viz logging in mesh_node forwarding

Cargo.lock

@@ -3202,6 +3202,18 @@ version = "2.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f8ca58f447f06ed17d5fc4043ce1b10dd205e060fb3ce5b979b8ed8e59ff3f79"
 
+[[package]]
+name = "mesh-viz-bridge"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+ "clap",
+ "futures-util",
+ "serde_json",
+ "tokio",
+ "tokio-tungstenite",
+]
+
 [[package]]
 name = "meshservice"
 version = "0.1.0"