feat(desktop): Gateway URL 配置化 + Rust panic hook 崩溃报告

- api-urls.ts: GATEWAY_URLS 读 VITE_GATEWAY_HTTP/WS env
- gateway-storage.ts: DEFAULT_GATEWAY_URL 读 VITE_GATEWAY_WS env
- lib.rs: 添加 tracing_subscriber 初始化 + panic::set_hook
  崩溃时自动写入 crash-reports/ 目录供诊断
- Cargo.toml: 添加 tracing-subscriber workspace 依赖

desktop/src-tauri/Cargo.toml

@@ -63,6 +63,7 @@ dashmap = { workspace = true }
 uuid = { workspace = true }
 base64 = { workspace = true }
 tracing = { workspace = true }
+tracing-subscriber = { workspace = true }
 secrecy = { workspace = true }
 
 # Browser automation (existing)