feat: implement BDD testing with Godog

Implement comprehensive BDD testing framework using Godog:
- Added feature files for greet and health endpoints
- Created test server that runs on port 9191
- Implemented step definitions using Godog's exact patterns
- Fixed undefined step warnings by following Godog conventions
- All tests passing with proper response validation
- Maintained black box testing principles

Key files:
- pkg/bdd/steps/steps.go - Step definitions using StepContext struct
- pkg/bdd/testserver/ - Test server implementation
- features/*.feature - BDD feature files
- pkg/bdd/README.md - Documentation for proper step patterns

The implementation follows Godog's exact pattern suggestions to avoid
undefined step warnings and provides comprehensive API testing.

features/bdd_test.go

@@ -0,0 +1,25 @@
+package features
+
+import (
+	"testing"
+
+	"DanceLessonsCoach/pkg/bdd"
+	"github.com/cucumber/godog"
+)
+
+func TestBDD(t *testing.T) {
+	suite := godog.TestSuite{
+		Name:                 "DanceLessonsCoach BDD Tests",
+		TestSuiteInitializer: bdd.InitializeTestSuite,
+		ScenarioInitializer:   bdd.InitializeScenario,
+		Options: &godog.Options{
+			Format:   "progress",
+			Paths:    []string{"."},
+			TestingT: t,
+		},
+	}
+
+	if suite.Run() != 0 {
+		t.Fatal("non-zero status returned, failed to run BDD tests")
+	}
+}

features/greet.feature

@@ -0,0 +1,13 @@
+# features/greet.feature
+Feature: Greet Service
+  The greet service should return appropriate greetings
+
+  Scenario: Default greeting
+    Given the server is running
+    When I request the default greeting
+    Then the response should be "{\"message\":\"Hello world!\"}"
+
+  Scenario: Personalized greeting
+    Given the server is running
+    When I request a greeting for "John"
+    Then the response should be "{\"message\":\"Hello John!\"}"

features/health.feature

@@ -0,0 +1,8 @@
+# features/health.feature
+Feature: Health Endpoint
+  The health endpoint should indicate server status
+
+  Scenario: Health check returns healthy status
+    Given the server is running
+    When I request the health endpoint
+    Then the response should be "{\"status\":\"healthy\"}"