[feature/backend] implement /users handler + switch to username + add display name + user management cli

backend/internal/handler/handler.go

@@ -34,6 +34,18 @@ func (h *Handler) RegisterRoutes(r *gin.Engine) {
 			auth.POST("/login", h.Login)
 		}
 
+		// User routes
+		users := api.Group("/users")
+		{
+			users.GET("", h.ListUsers)
+			users.POST("", h.CreateUser)
+			users.GET("/:id", h.GetUser)
+			users.PUT("/:id", h.UpdateUser)
+			users.DELETE("/:id", h.DeleteUser)
+			users.GET("/me", h.GetCurrentUser)
+			users.PUT("/me", h.UpdateCurrentUser)
+		}
+
 		// Category routes
 		categories := api.Group("/categories")
 		{