docs: switch fetch commands to rb.godwinsystems.com

The ops -> godwinsystems org move would have made every hand-typed onsite
command 10 characters longer, against the whole reason filenames here are
short. A redirect host makes them shorter than they ever were:

  irm https://gitea.ivangodwin.com/ops/rb/raw/branch/main/od-smb-cred.md
  irm rb.godwinsystems.com/od-smb-cred.md

Flips all 6 hardcoded URLs and documents what the hostname is, where the
route is defined, and that removing it means updating these commands in
the same change.

Verified before committing: the short and canonical URLs return
byte-identical content for 5 files, the scheme-less http:// form resolves
through 301 -> 302 -> 200, bare / lands on the repo page, and a missing
file still 404s at the right path.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HwcG1jLs1T425QRMxtjxP7

od-backup-schedule.md

@@ -67,7 +67,7 @@ schtasks /Create /TN "OD Backup Health Check" ^
 The check is **read-only** — no DB, no service, no file changes — so it's safe to run any time, including a manual spot-check:
 
 ```
-irm https://gitea.ivangodwin.com/ops/rb/raw/branch/main/scripts/od-backup-check.ps1 | iex
+irm rb.godwinsystems.com/scripts/od-backup-check.ps1 | iex
 ```
 
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