* fix(master): route ec shard vids to NewEcVids on initial subscribe
ToVolumeLocations appended EC shard volume IDs to NewVids, so a freshly
subscribing master client registered them in the regular-volume map via
addLocation instead of addEcLocation until the next heartbeat-driven
delta arrived. Append to NewEcVids to match the incremental path.
Fixes#9429
* fix(master): dedupe ec vids in initial subscribe snapshot
dn.GetEcShards returns per-(vid, diskId) entries, so a single EC volume
spread across multiple physical disks on one DataNode emitted the same
vid multiple times in NewEcVids. Dedupe so the snapshot carries each
vid once.