download: Support all other "registered" instances shortcuts

[yarikoptic]

This came in the course of work on

• Add vendorization support dandi-archive#2584

ATM we support only DANDI: even though we know about "ember" and "linc" instances and in principle could support them:

❯ dandi download EMBER:000005
2025-10-08 11:51:45,388 [    INFO] Logs saved in /home/yoh/.local/state/dandi-cli/log/2025.10.08-15.51.44Z-1473989.log
Error: We do not know how to map URL EMBER:000005 to our servers.
Accepted resource identifier patterns:
 - DANDI:<dandiset id>[/<version>]
 - https://gui.dandiarchive.org/...
...
❯ dandi --version
0.71.4+6.gb0b07c66

I think it makes sense to support all known instances. Although we might also "sync" it only to support the ones with identifiers.org (hence I think no LINC?).

After this implemented, then server could add support to generate shortened link, but it would need to know what instances dandi-cli supports which makes it somewhat tricky without hardcoding.