P2R-02 follow-up: schedule Run-now feedback (single → job log, multi → toast)

Schedules tab Run-now used to silently HX-Redirect back to the
list, leaving the operator wondering whether the click registered.
Now:

* Single-source-group schedule → HX-Redirect to that one job's
  live log, matching the per-source-group Run-now UX from Sources.
* Multi-group schedule → stay on the schedules list and fire a
  success toast ("N backups dispatched: <group names>") via the
  existing rm:toast HX-Trigger channel, so the operator sees clear
  acknowledgement without losing their place.

dispatchBackupForGroup now returns the persisted job ID so the
caller can choose between job-log redirect and toast feedback;
on any internal failure it returns "" and the warning still
hits slog as before. The cron-fired path (dispatchScheduledJob)
ignores the return value, behaviour unchanged.

internal/server/http/schedule_push.go

@@ -167,7 +167,12 @@ func (s *Server) dispatchScheduledJob(ctx context.Context, hostID string, conn *
 // dispatchBackupForGroup builds and sends a single backup command.run
 // envelope on conn for the given group. Persists the job row first so
 // the live log viewer can subscribe to it.
-func (s *Server) dispatchBackupForGroup(ctx context.Context, conn *ws.Conn, hostID, scheduleID string, g *store.SourceGroup, scheduledAt time.Time) {
+// dispatchBackupForGroup persists a backup job row, sends the
+// command.run envelope to the agent, and audit-logs the dispatch.
+// Returns the persisted job ID on success, or "" on any failure
+// (failures are slog.Warn-ed). Callers may use the returned ID to,
+// e.g., redirect the UI to the live job log.
+func (s *Server) dispatchBackupForGroup(ctx context.Context, conn *ws.Conn, hostID, scheduleID string, g *store.SourceGroup, scheduledAt time.Time) string {
 	jobID := ulid.Make().String()
 	now := time.Now().UTC()
 	scheduleRef := scheduleID
@@ -181,7 +186,7 @@ func (s *Server) dispatchBackupForGroup(ctx context.Context, conn *ws.Conn, host
 	}); err != nil {
 		slog.Warn("schedule.fire: persist job", "host_id", hostID,
 			"schedule_id", scheduleID, "group", g.Name, "err", err)
-		return
+		return ""
 	}
 	// Backup ignores RetentionPolicy — the forget cadence lives on
 	// host_repo_maintenance and is driven by the server-side ticker
@@ -196,14 +201,14 @@ func (s *Server) dispatchBackupForGroup(ctx context.Context, conn *ws.Conn, host
 	if err != nil {
 		slog.Warn("schedule.fire: marshal command.run",
 			"host_id", hostID, "schedule_id", scheduleID, "err", err)
-		return
+		return ""
 	}
 	sendCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
 	defer cancel()
 	if err := conn.Send(sendCtx, env); err != nil {
 		slog.Warn("schedule.fire: send command.run",
 			"host_id", hostID, "schedule_id", scheduleID, "err", err)
-		return
+		return ""
 	}
 	_ = s.deps.Store.AppendAudit(ctx, store.AuditEntry{
 		ID:         ulid.Make().String(),
@@ -216,4 +221,5 @@ func (s *Server) dispatchBackupForGroup(ctx context.Context, conn *ws.Conn, host
 	slog.Info("schedule.fire: dispatched backup",
 		"host_id", hostID, "schedule_id", scheduleID,
 		"group", g.Name, "job_id", jobID, "scheduled_at", scheduledAt)
+	return jobID
 }