seo: Quest detail pages use static, generic metadata instead of the real quest title/description

[LarytheLord]

app/quests/[id]/layout.tsx exports static metadata ("Quest Details — Guild") instead of a generateMetadata() function pulling the actual quest's title/description. Every quest page looks identical to search engines and link previews, losing the long-tail SEO value of dozens of distinct quest pages.

Acceptance Criteria

• Convert to generateMetadata({ params }) that fetches the quest and sets a real title/description per page
• Falls back gracefully if the quest isn't found