Expose the protected phrase extraction pipeline through the web UI:
- Admin routes: POST /admin/build-phrases, /admin/generate-ngrams, and
/admin/judge-ngrams, each wrapping the protected_phrases.lib backfill
helpers, committing on success, rolling back and rendering an error
partial on failure, and reporting per-book/candidate/mention counts.
- Book detail page: show candidate, judged, and protected phrase counts,
list top candidate n-grams (with kept/rejected status) and protected
phrases, and add a POST /books/{id}/recalculate-phrases action that
clears and regenerates candidates, then redirects back with a status
message.
- Admin template: add Generate/Judge n-gram buttons.
Also reflows admin.html to 2-space HTML formatting.
Richie