kms-website: 3-up KMS_AUTO quick-start cards + save-as downloads + clean script comments

- Replace single interactive one-liner with three side-by-side cards
  (Windows / Office+Project+Visio / Both) using $env:KMS_AUTO=...; the
  contract is already supported by kms-bootstrap.ps1
- Make Downloads links use the 'download' attribute so browsers prompt
  save-as instead of rendering .ps1 as text
- Strip operator-side framing: kms-bootstrap.ps1 no longer says
  "this activation has been logged" and both scripts now point Source
  at the public mirror instead of forgejo.viktorbarzin.me

static/scripts/setup-kms.ps1

@@ -10,7 +10,7 @@
 # Or with a custom KMS host (e.g. self-hosted):
 #   $env:KMS_HOST = 'kms.example.com'; iwr ... | iex
 #
-# Source: https://forgejo.viktorbarzin.me/viktor/kms-website
+# Source: https://kms.viktorbarzin.me/scripts/setup-kms.ps1
 # Licence: MIT, no warranty, KMS activates Volume License SKUs only.
 
 [CmdletBinding()]