[Agent] Sitemap lists URLs for disabled portal features

Agent brief

Category: bug | Severity: medium | Effort: M

Problem

Sitemap always emits /changelog, /leaderboard, etc. for every public project via static PROJECT_SURFACES. Disabled features produce 404 URLs indexed by crawlers.

Repro

1. Disable changelog or leaderboard
2. Check /sitemap.xml — dead URLs still listed

Files

• src/lib/seo/sitemap.ts — PROJECT_SURFACES
• src/lib/seo/sitemap-data.ts — include project flags

Acceptance criteria

• Sitemap omits /changelog when changelog_enabled=false
• Sitemap omits /leaderboard when disabled
• Update sitemap.test.ts

Suggested approach

Filter surfaces per-project in buildProjectSurfaceEntries using flags from DB.