feat(ebook): add admin and book-detail UI for protected phrase pipeline

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.

python/ebook_search/api/routes/admin.py

@@ -14,6 +14,11 @@ from python.ebook_search.api.dependencies import (
 from python.ebook_search.api.web import templates
 from python.ebook_search.embeddings import embed_missing_chunks, embedding_model_stats
 from python.ebook_search.ingest import ingest_configured_paths
+from python.ebook_search.protected_phrases.lib import (
+    build_missing_protected_phrases,
+    generate_candidate_phrases_for_books,
+    judge_candidate_phrases_for_books,
+)
 from python.fastapi_tools import DbSession  # noqa: TC001 FastAPI resolves this annotated dependency at runtime
 
 logger = logging.getLogger(__name__)
@@ -45,6 +50,97 @@ def scan_library(request: Request, config: AppConfig, session: DbSession) -> HTM
     return templates.TemplateResponse(request, "partials/admin_status.html", {"message": f"Indexed {count} EPUBs"})
 
 
+@router.post("/build-phrases", response_class=HTMLResponse)
+def build_phrases(request: Request, config: AppConfig, session: DbSession) -> HTMLResponse:
+    """Build protected phrases for indexed books that are missing them."""
+    try:
+        result = build_missing_protected_phrases(session, config)
+        session.commit()
+    except Exception as error:
+        session.rollback()
+        logger.exception("ebook_admin_build_phrases_failed")
+        return templates.TemplateResponse(request, "partials/error.html", {"message": str(error)}, status_code=500)
+
+    logger.info(
+        "ebook_admin_build_phrases_complete books_seen=%s books_built=%s protected=%s mentions=%s",
+        result.books_seen,
+        result.books_built,
+        result.protected_phrases,
+        result.phrase_mentions,
+    )
+    return templates.TemplateResponse(
+        request,
+        "partials/admin_status.html",
+        {
+            "message": (
+                f"Built phrases for {result.books_built} of {result.books_seen} books; "
+                f"{result.protected_phrases} protected phrases, {result.phrase_mentions} mentions"
+            )
+        },
+    )
+
+
+@router.post("/generate-ngrams", response_class=HTMLResponse)
+def generate_ngrams(request: Request, config: AppConfig, session: DbSession) -> HTMLResponse:
+    """Generate candidate n-grams for indexed books without LLM judging."""
+    try:
+        result = generate_candidate_phrases_for_books(session, config)
+        session.commit()
+    except Exception as error:
+        session.rollback()
+        logger.exception("ebook_admin_generate_ngrams_failed")
+        return templates.TemplateResponse(request, "partials/error.html", {"message": str(error)}, status_code=500)
+
+    logger.info(
+        "ebook_admin_generate_ngrams_complete books_seen=%s books_built=%s candidates=%s",
+        result.books_seen,
+        result.books_built,
+        result.candidate_phrases,
+    )
+    return templates.TemplateResponse(
+        request,
+        "partials/admin_status.html",
+        {
+            "message": (
+                f"Generated n-grams for {result.books_built} of {result.books_seen} books; "
+                f"{result.candidate_phrases} candidates stored"
+            )
+        },
+    )
+
+
+@router.post("/judge-ngrams", response_class=HTMLResponse)
+def judge_ngrams(request: Request, config: AppConfig, session: DbSession) -> HTMLResponse:
+    """Judge stored candidate n-grams and promote accepted protected phrases."""
+    try:
+        result = judge_candidate_phrases_for_books(session, config)
+        session.commit()
+    except Exception as error:
+        session.rollback()
+        logger.exception("ebook_admin_judge_ngrams_failed")
+        return templates.TemplateResponse(request, "partials/error.html", {"message": str(error)}, status_code=500)
+
+    logger.info(
+        "ebook_admin_judge_ngrams_complete books_seen=%s books_judged=%s candidates_judged=%s protected=%s mentions=%s",
+        result.books_seen,
+        result.books_judged,
+        result.candidates_judged,
+        result.protected_phrases,
+        result.phrase_mentions,
+    )
+    return templates.TemplateResponse(
+        request,
+        "partials/admin_status.html",
+        {
+            "message": (
+                f"Judged {result.candidates_judged} candidates across {result.books_judged} of "
+                f"{result.books_seen} books; {result.protected_phrases} protected phrases, "
+                f"{result.phrase_mentions} mentions"
+            )
+        },
+    )
+
+
 @router.post("/embed-missing", response_class=HTMLResponse)
 def embed_missing(request: Request, config: AppConfig, session: DbSession) -> HTMLResponse:
     """Embed chunks missing vectors for the configured model."""