get_memory_trend: join the grants series so total_granted_mb carries real data (complete fix for #3529) #3548

#3529 shipped the minimal honest fix: total_granted_mb is an explicit null with a granted_note naming get_memory_grants, on both SKUs. The complete fix from that issue remains open: join the memory-grant series both stores already collect (Lite's LocalDataService.MemoryGrants.cs read; Darling's grants table) into the trend payload so the field carries real data.

Both SKUs together, identical shape, and drop the null + note once the join lands. The viewer charts already overlay exactly this series, so the read exists on both sides.