Add SEO title overrides for docs pages

[tudddorrr]

SEO title overrides

• Added an optional seoTitle frontmatter field so docs pages can serve a more descriptive <title> to search engines without changing their visible page name.
• Page titles now use seoTitle when present, falling back to the existing title, and append | Talo docs.

Title handling

• Introduced a shared docTitle helper in app/lib/seo.ts and reused it in the docs route.
• The 1.x docs landing page keeps the marketing homepage title, while every other page gets the SEO suffix.

Content coverage

• Populated seoTitle across Godot, Unity, HTTP, sockets, admin, integrations and self-hosting docs for both 1.x and pre-1.0, adding technology prefixes and clearer phrasing.
• Added missing descriptions to the socket common errors pages.