Refactor to JSON API with Chi router and interface-based design

- Add pkg/greet/api_v1.go with ApiV1Greet interface and handler
- Implement Greeter interface for dependency injection
- Return JSON responses with proper Content-Type headers
- Move greet service instantiation to server package
- Separate v1 route registration into registerApiV1Routes function
- Health endpoint at /api level, greet endpoints at /api/v1/greet
- Simplify server entrypoint by removing external dependencies

cmd/server/main.go

@@ -0,0 +1,15 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+
+	"DanceLessonsCoach/pkg/server"
+)
+
+func main() {
+	server := server.NewServer()
+
+	fmt.Println("Server running on :8080")
+	http.ListenAndServe(":8080", server.Router())
+}