Add per-request AI logging, DB batch queue, WS entity updates, and UI polish

- log_thread.py: thread-safe ContextVar bridge so executor threads can log
  individual LLM calls and archive searches back to the event loop
- ai_log.py: init_thread_logging(), notify_entity_update(); WS now pushes
  entity_update messages when book data changes after any plugin or batch run
- batch.py: replace batch_pending.json with batch_queue SQLite table;
  run_batch_consumer() reads queue dynamically so new books can be added
  while batch is running; add_to_queue() deduplicates
- migrate.py: fix _migrate_v1 (clear-on-startup bug); add _migrate_v2 for
  batch_queue table
- _client.py / archive.py / identification.py: wrap each LLM API call and
  archive search with log_thread start/finish entries
- api.py: POST /api/batch returns {already_running, added}; notify_entity_update
  after identify pipeline
- models.default.yaml: strengthen ai_identify confidence-scoring instructions;
  warn against placeholder data
- detail-render.js: book log entries show clickable ID + spine thumbnail;
  book spine/title images open full-screen popup
- events.js: batch-start handles already_running+added; open-img-popup action
- init.js: entity_update WS handler; image popup close listeners
- overlays.css / index.html: full-screen image popup overlay
- eslint.config.js: add new globals; fix no-redeclare/no-unused-vars for
  multi-file global architecture; all lint errors resolved

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

static/css/overlays.css

@@ -29,3 +29,10 @@
 .pq-skip-btn{background:rgba(255,255,255,.1);color:#cbd5e1;border:none;border-radius:8px;padding:12px 18px;font-size:.85rem;cursor:pointer;min-width:70px}
 .pq-skip-btn:active{background:rgba(255,255,255,.2)}
 .pq-processing{position:absolute;inset:0;background:rgba(15,23,42,.88);display:flex;align-items:center;justify-content:center;flex-direction:column;gap:10px;font-size:.9rem}
+
+/* ── Image popup ── */
+.img-popup{display:none;position:fixed;inset:0;background:rgba(0,0,0,.75);z-index:500;align-items:center;justify-content:center}
+.img-popup.open{display:flex}
+.img-popup-inner{position:relative;max-width:90vw;max-height:90vh}
+.img-popup-inner img{max-width:90vw;max-height:90vh;object-fit:contain;border-radius:4px;display:block}
+.img-popup-close{position:absolute;top:-14px;right:-14px;background:#fff;border:none;border-radius:50%;width:28px;height:28px;cursor:pointer;font-size:18px;line-height:28px;text-align:center;padding:0;box-shadow:0 2px 6px rgba(0,0,0,.3)}