Finalize maintenance routing and documentation updates

[sk9-devops]

Summary

• Clarifies maintenance routing behavior for both albGroupName and targetIngress modes.
• Documents AWS Load Balancer Controller IAM prerequisites and troubleshooting for ALB listener rule reconciliation.
• Enhances the GitHub Pages landing page with clearer purpose messaging, copyable install/configuration snippets, structured data, dark-mode support, and an architecture flow diagram.
• Removes GitHub star badges from the landing page for a cleaner product-focused presentation.

Dependabot / Security Scope

This PR includes the previously approved high-priority dependency/security bump already present on this branch:

• google.golang.org/grpc and related transitive Go module updates

No additional Dependabot changes were added during the latest docs/site update.

Validation

• custom-gcl passed with 0 issues
• go test ./... passed
• git diff --check passed
• Verified landing-page copy targets resolve to existing IDs
• Verified no duplicate HTML IDs
• Verified JSON-LD parses successfully