Issue 4: Implement Public Blog Routes, RSS, Sitemap, and SEO #540

Parent Epic: #536
Depends on: #537, #538, #539

Objective

Expose published blog content safely through public routes, RSS, sitemap, and SEO metadata rendering.

Context

This issue makes blog_content usable on the public website while enforcing strict public visibility rules. Public routes must never leak draft, review, scheduled-future, archived, private, unlisted, or soft-deleted content.

Scope

• Public blog index
• Public post detail page
• Public category archive
• Public tag archive
• Public search
• RSS feed
• Blog sitemap
• SEO metadata rendering
• Canonical URL validation
• Safe content rendering

Out of Scope

• Admin UI
• Revision restore UI
• Template/widget/menu/ads advanced rendering unless implemented in a later issue
• Comment system
• Public user registration

Routes

GET /blog
GET /blog/[slug]
GET /blog/category/[slug]
GET /blog/tag/[slug]
GET /blog/search?q=
GET /feed.xml
GET /sitemap-blog.xml

Public Visibility Rule

All public queries must centralize and reuse this predicate:

status = 'published'
AND visibility = 'public'
AND deleted_at IS NULL
AND published_at IS NOT NULL
AND published_at <= now()

Additional listing/search/feed/sitemap rule:

visibility != 'unlisted'

SEO Requirements

• Render seo_title when available.
• Fall back to title when seo_title is empty.
• Render meta_description when available.
• Fall back to excerpt or safe generated summary when meta_description is empty.
• Render canonical URL only when valid and safe.
• Do not render unsafe URLs.

RSS Requirements

• RSS must include only published public content.
• RSS must exclude unlisted, private, archived, scheduled-future, draft, review, and deleted content.
• RSS must respect tenant context and blog settings.

Sitemap Requirements

• Sitemap must include only published public content.
• Sitemap must exclude unlisted, private, archived, scheduled-future, draft, review, and deleted content.
• Sitemap must respect tenant context and blog settings.

Content Safety Requirements

• Use structured JSON content as the source of truth.
• Rendering must sanitize or safely render content.
• Script tags must be rejected or stripped.
• Inline JavaScript must be rejected or stripped.
• Dangerous iframe/embed content must be rejected or stripped.
• Unsafe URLs must be rejected.
• Error output must not expose stack traces.

Acceptance Criteria

• Public blog index exists.
• Public post detail route exists.
• Public category archive exists.
• Public tag archive exists.
• Public search exists.
• RSS feed exists.
• Blog sitemap exists.
• Public query helper centralizes the visibility predicate.
• Draft content is never publicly visible.
• Review content is never publicly visible.
• Scheduled-future content is never publicly visible.
• Archived content is never publicly visible.
• Private content is never publicly visible.
• Unlisted content is excluded from listing/search/feed/sitemap.
• Soft-deleted content is never publicly visible.
• Public post detail renders SEO title and meta description.
• Canonical URL is rendered only when valid.
• RSS includes only published public content.
• Sitemap includes only published public content.
• Content rendering is sanitized.
• Tests cover public visibility leakage.
• Tests cover SEO rendering.
• Tests cover RSS and sitemap content filtering.
• bun run build passes.

Validation Commands

bun run test
bun run typecheck
bun run build