fix(search): load Pagefind from same-origin base path

[Puppo]

Summary

• load Pagefind through the configured base path so root deployments request /pagefind/pagefind.js
• reset and report failed Pagefind initialization
• correct the documented production build command

Testing

• npm run lint
• npm run check
• Astro/Vite static build completed and emitted /pagefind/pagefind.js with no //pagefind/pagefind.js

Pagefind's bundled ARM64 indexer cannot run in this 16 KB-page container (jemalloc: Unsupported system page size), so the full production build could not complete locally.