Add browser deploy recon backend with port scan, web crawl, and deploy lane recommendations.

POST /api/v1/recon/scan probes fleet ports from the server host, crawls owned HTTP targets, maps findings to spread lanes, and records optional oath ledger rows.

server/internal/api/spread_handler.go

@@ -26,6 +26,7 @@ type SpreadHandler struct {
 	publicURL         func() string
 	erasureShards     *erasure.ShardStore
 	deployPlan        *DeployPlanHandler
+	allowlistFn       func() map[string]ServiceDeployLane
 	policyPathTracer  *PathTracerHandler
 	policyFanoutCfgFn func() PolicyFanoutConfig
 	notesMu     sync.RWMutex