Implement canonical_redirect helper in content.py to enforce slug-based 301 redirects for gist, news, post, and project detail pages. Add first_image_url helper to extract primary image from item or attachments for Open Graph meta tags. Inject next_page_url into feed, gists, news, and projects list page SEO contexts for pagination link rel. Extend seo.py with SITEMAP_URL_LIMIT, SITEMAP_TTL constants and _sitemap cache variable for future sitemap generation optimization. Update profile page to raise 404 via not_found instead of 302 redirect, and include og_image from avatar_url.
Introduce a new `/leaderboard` endpoint ranking top 50 members by total stars, wire it into the app router and documentation. Implement `_backfill_gamification()` in `database.py` to compute XP/levels for existing accounts from prior posts, comments, votes, and follows. Extract `is_owner()`, `create_content_item()`, and `detail_context()` into `content.py` to centralize content creation, reward awarding, mention notifications, and attachment linking. Update comment creation/deletion in `comments.py` to use `award_rewards()` with `XP_COMMENT` and the new `is_owner()` helper. Add shared template partials documentation for vote bars, star buttons, post headers, and topic selectors to `AGENTS.md`.
