feat(server): step usage counts endpoint

server/internal/api/workflows.go

@@ -23,6 +23,7 @@ func registerWorkflowRoutes(g *gin.RouterGroup) {
 	g.GET("/steps/:id/export", exportStep)
 	g.POST("/steps/import", importStep)
 	g.POST("/steps/seed-defaults", seedDefaults)
+	g.GET("/steps/usage", stepUsage)
 	g.POST("/steps/parse", parseStep)
 
 	g.GET("/workflows", listWorkflows)
@@ -154,6 +155,15 @@ func listSteps(c *gin.Context) {
 	c.JSON(http.StatusOK, steps)
 }
 
+func stepUsage(c *gin.Context) {
+	counts, err := services.StepUsageCounts()
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+		return
+	}
+	c.JSON(http.StatusOK, counts)
+}
+
 func createStep(c *gin.Context) {
 	var s models.WorkflowStep
 	if err := c.ShouldBindJSON(&s); err != nil {