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/handlers.go

@@ -0,0 +1,36 @@
+package handlers
+
+import (
+	"net/http"
+
+	"github.com/andyleap/hnh-map/internal/app"
+	"github.com/andyleap/hnh-map/internal/app/services"
+)
+
+// Handlers holds HTTP handlers and their dependencies.
+type Handlers struct {
+	App   *app.App
+	Auth  *services.AuthService
+	Map   *services.MapService
+	Admin *services.AdminService
+}
+
+// New creates Handlers with the given dependencies.
+func New(a *app.App, auth *services.AuthService, mapSvc *services.MapService, admin *services.AdminService) *Handlers {
+	return &Handlers{App: a, Auth: auth, Map: mapSvc, Admin: admin}
+}
+
+// requireAdmin returns session if admin, or writes 401 and returns nil.
+func (h *Handlers) requireAdmin(rw http.ResponseWriter, req *http.Request) *app.Session {
+	s := h.Auth.GetSession(req)
+	if s == nil || !s.Auths.Has(app.AUTH_ADMIN) {
+		JSONError(rw, http.StatusUnauthorized, "Unauthorized", "UNAUTHORIZED")
+		return nil
+	}
+	return s
+}
+
+// canAccessMap returns true if session has map or admin auth.
+func (h *Handlers) canAccessMap(s *app.Session) bool {
+	return s != nil && (s.Auths.Has(app.AUTH_MAP) || s.Auths.Has(app.AUTH_ADMIN))
+}