feat(observability): add maintenance policy metrics

Prometheus: runs, duration, rows_deleted, config_changes; инкремент при CRUD и Execute.
Co-authored-by: Cursor <[email protected]>

internal/httpapi/routes_maintenance.go

@@ -6,6 +6,7 @@ import (
 	"strings"
 
 	"evobgp/internal/jobs"
+	"evobgp/internal/observability"
 	"evobgp/internal/store"
 )
 
@@ -107,6 +108,7 @@ func (s *Server) handleCreateMaintenancePolicy(w http.ResponseWriter, r *http.Re
 		return
 	}
 	_ = s.store.AppendMaintenancePolicyConfigAudit(actorPrefix(a), p.ID, "create", nil, maintenancePolicyJSON(p))
+	observability.IncMaintenanceConfigChange("create")
 	s.reloadMaintenanceConfig(r)
 	writeJSON(w, http.StatusCreated, maintenancePolicyJSON(p))
 }
@@ -133,6 +135,7 @@ func (s *Server) handlePatchMaintenancePolicy(w http.ResponseWriter, r *http.Req
 		return
 	}
 	_ = s.store.AppendMaintenancePolicyConfigAudit(actorPrefix(a), id, "update", maintenancePolicyJSON(before), maintenancePolicyJSON(updated))
+	observability.IncMaintenanceConfigChange("update")
 	s.reloadMaintenanceConfig(r)
 	writeJSON(w, http.StatusOK, maintenancePolicyJSON(updated))
 }
@@ -153,6 +156,7 @@ func (s *Server) handleDeleteMaintenancePolicy(w http.ResponseWriter, r *http.Re
 		return
 	}
 	_ = s.store.AppendMaintenancePolicyConfigAudit(actorPrefix(a), id, "delete", maintenancePolicyJSON(before), nil)
+	observability.IncMaintenanceConfigChange("delete")
 	s.reloadMaintenanceConfig(r)
 	w.WriteHeader(http.StatusNoContent)
 }