feat: add networking module with TCP Socket/Server and example applications

Implement a full-featured `net` module supporting TCP `Socket` and `Server` classes via libuv, including example applications (chat server, echo server, HTTP client/server, file explorer, system dashboard) and benchmark scripts (fibonacci, n-body). Add GEMINI.md project documentation and Stderr class to io module.

example/benchmark/fib.wren

@@ -0,0 +1,15 @@
+import "os" for Process
+
+var start = System.clock
+
+var fib
+fib = Fn.new { |n|
+  if (n < 2) return n
+  return fib.call(n - 1) + fib.call(n - 2)
+}
+
+for (i in 1..5) {
+  System.print("fib(28) = " + fib.call(28).toString)
+}
+
+System.print("Elapsed: " + (System.clock - start).toString + "s")