feat(server): keep monitors and in-flight runs going when a licence lapses

Monitor execution and the workflow runner are deliberately unguarded: billing
state must not take away a customer's ability to know their infrastructure is
on fire, and killing a run midway leaves a half-configured server.

The plan called for a server-limit check in gRPC Register. Left out: a server
row only comes from CreateServer, which already checks the cap, so counting in
Register counts the caller itself and would reject a legitimate agent at
exactly the cap.

server/internal/services/workflow_runner.go

@@ -202,6 +202,9 @@ func runServer(instanceID, runID string, srvIdx int, steps []models.ResolvedStep
 	allSecrets := map[string]string{}
 	serverFailed := false
 
+	// A run already in flight when the licence expires finishes its remaining
+	// steps. New runs are blocked at the API, but killing a workflow midway leaves
+	// a server in a half-configured state, which is worse than letting it complete.
 	for i, step := range steps {
 		startStep(runID, serverID, i, "running")
 		stepStart := time.Now()