Update project structure and enhance frontend functionality

- Added a new AGENTS.md file to document the project structure and conventions.
- Updated .gitignore to include node_modules and refined cursor rules.
- Introduced new backend and frontend components for improved map interactions, including context menus and controls.
- Enhanced API composables for better admin and authentication functionalities.
- Refactored existing components for cleaner code and improved user experience.
- Updated README.md to clarify production asset serving and user setup instructions.

internal/app/handlers/response.go

@@ -0,0 +1,17 @@
+package handlers
+
+import (
+	"net/http"
+
+	"github.com/andyleap/hnh-map/internal/app/response"
+)
+
+// JSON writes v as JSON with the given status code.
+func JSON(rw http.ResponseWriter, status int, v any) {
+	response.JSON(rw, status, v)
+}
+
+// JSONError writes an error response in standard format.
+func JSONError(rw http.ResponseWriter, status int, msg, code string) {
+	response.JSONError(rw, status, msg, code)
+}