docs: add dark-mode screenshot variants to xc-configuration pages

[robinmordasiewicz]

Summary

xc-configuration.mdx has 4 Screenshot components with only a light= prop. One screenshot on the same page (csd-injected-scripts-dark.png at line 70) already has a correct dark variant — that pattern should be applied to the remaining 4.

Affected files

File	Line	Image	Action
docs/xc-configuration.mdx	22	csd-config.png	Add dark= variant
docs/xc-configuration.mdx	42	csd-lb-config.png	Add dark= variant
docs/xc-configuration.mdx	47	csd-lb-csd-settings.png	Add dark= variant
docs/xc-configuration.mdx	52	csd-lb-injection-scope.png	Add dark= variant

Resolution

1. Capture dark-mode screenshots of each XC Console configuration view
2. Save as *-dark.png in docs/images/
3. Update each Screenshot component to include dark="/images/<name>-dark.png"

Correct example already in this file (line 70):

<Screenshot
  light="/images/csd-injected-scripts-light.png"
  dark="/images/csd-injected-scripts-dark.png"
  alt="Injected scripts in DevTools Elements tab"
/>

Source

Identified by F5 brand compliance review (f5xc-brand:brand-reviewer skill).