refactor(server): strictly enforce CLI port argument for bind, dropping MCP_PORT env var fallback

stub/tests/e2e.rs

@@ -59,6 +59,8 @@ async fn test_full_system_e2e_performance() {
     // 1. Start Server
     let _server = ChildGuard(
         Command::new(&server_exe)
+            .arg("--port")
+            .arg(test_port)
             .env("MCP_PORT", test_port)
             .env("RUST_LOG", "debug")
             .env("MCP_MEMORY_STORE_DIR", temp_dir.to_str().unwrap())