Point GitHub URLs at omacom/omarchy instead of basecamp/omarchy

The repo moved to the omacom org. GitHub redirects the old URLs, but
`omarchy channel set dev` was still cloning from basecamp/omarchy, which
left every dev checkout with a stale origin remote that confuses gh
(pr create fails with "No commits between omacom:quattro and
basecamp:<branch>"). Update the clone URL, the quattro upgrade tarball,
the update-confirm release link, the systemd Documentation link, and
the manual.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LSFKDatumRZHB8zqk5CP5C

default/systemd/user/omarchy-speaker-tuning.service

@@ -1,6 +1,6 @@
 [Unit]
 Description=Omarchy speaker tuning filter-chain
-Documentation=https://github.com/basecamp/omarchy/blob/master/docs/audio-tuning.md
+Documentation=https://github.com/omacom/omarchy/blob/master/docs/audio-tuning.md
 # WirePlumber does the linking, so starting before it is up risks the output being
 # linked before the speaker device has been discovered.
 After=pipewire.service wireplumber.service