Enable disabled features

Re-enable features that were temporarily disabled or mocked during the initial project setup.

Disabled Routes

Routes that were moved to src/lib/disabled-routes/:

• feed.json - JSON feed endpoint — restored
• feed.xml - RSS/Atom feed endpoint — restored
• sitemap-appendix.xml - Sitemap XML endpoint — restored
• og/ - Dynamic OG image generation — separate todo
• sitemap/ - Sitemap page — restored

Mocked Features

• src/routes/+layout.server.js - Feed fetch returns empty { items: [] } — restored, fetches from /feed.json
• src/routes/+layout.server.js - Module scanning commented out — restored
• src/routes/+layout.svelte - Feed links commented out — separate todo
• src/lib/Meta.svelte - OG image uses cover directly instead of generated image — separate todo
• src/lib/Articles.svelte - Uses feed?.items ?? [] fallback — acceptable now that feed is live

Remaining

• Restore dynamic OG image generation
• Add feed link tags to layout