Refactor domain references from ruska.ai to mifune.dev

[ryaneggz]

Summary

Refactor the website from ruska.ai branding/domain references to mifune.dev.

Scope

• Replace visible copy, metadata, config, links, canonical URLs, and environment defaults that reference ruska.ai.
• Update any docs or deployment configuration where the public site/domain is referenced.
• Verify no stale ruska.ai references remain unless intentionally preserved for redirects or legacy compatibility.

Acceptance Criteria

• The site consistently uses mifune.dev in user-facing content and metadata.
• Search confirms no unintended ruska.ai references remain.
• Build/test/lint checks pass for the website.