feat: implement dynamic server list loading from API

Add internal/api package to fetch server list from /api/servers.json endpoint

Replace hardcoded server list with dynamic API call

Implement loading states, error handling, and refresh capability

internal/ui/screens/screens_test.go

@@ -0,0 +1,10 @@
+// package screens implements application screens (login, main menu, settings).
+package screens
+
+import "testing"
+
+// Dummy test to ensure package compiles
+func TestScreensPackage_Compiles(t *testing.T) {
+	// This test ensures the screens package compiles without errors
+	// We're not testing the actual UI output as that requires a GUI environment
+}