docs: update main domain semaphoreci.com → semaphore.io (fixes #472)

[mohankrishnaalavala]

📝 Description

Title: docs: switch main-site links to semaphore.io (fixes #472)

Summary
Replace root-domain semaphoreci.com with semaphore.io across docs.
Keep emails (@semaphoreci.com) and subdomains (docs/id/status.semaphoreci.com) intact.
No code or tests changed.

✅ Checklist

• [Yes ] I have tested this change
• This change requires documentation update

Testing done

• Verified no remaining root-domain refs:
  • git grep -n 'https?://(www.)?semaphoreci.com\b' → none
  • git grep -nP '(?<![@.])\bsemaphoreci.com\b(?!/)' → none
• Confirmed subdomains/emails remain unchanged:
  • docs/id/status.semaphoreci.com and *@semaphoreci.com still present
• Intentionally left Kubernetes label namespace keys like
  semaphoreci.com/resource-type unchanged.

[lucianoliberti]

@mohankrishnaalavala can you please sign your commit and also rebase the branch to resolve the conflicts? We're sorry for the late response, thanks!

[lucianoliberti]

hi @mohankrishnaalavala can you please sign your commit and also rebase the branch to resolve the conflicts? We're sorry for the late response