feat(bulk): consensus ML suggestions + frontend polish

Bulk editor now loads consensus ML suggestions across the current
selection via a new POST /api/suggestions/bulk endpoint, powered by
get_bulk_suggestions() in tag_suggestions.py. A tag is surfaced only if
it was suggested for or already applied to >= 80% of the selection;
coverage counts include images that already have the tag so a near-
universal tag isn't penalized for dropping out of suggestion lists.
Accept-only chips (no reject) match the rest of the suggestions UX.

Frontend polish in the same commit:
- Showcase session dedup (exclude seen ids, reset on second lap) and
  aspect-ratio-aware placeholder heights for better column balancing
- Modal touch-swipe navigation on the image wrapper, auto-focus of the
  tag input on desktop (>=768px), and autocomplete flip-up when the
  dropdown would cover the Suggestions section
- Settings template inline styles replaced with utility classes
- Inline series-editor script extracted to gallery-series-editor.js

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/static/js/bulk-select.js

@@ -32,6 +32,8 @@
     dom.tagInput = document.getElementById('bulkTagInput');
     dom.autocomplete = document.getElementById('bulkTagAutocomplete');
     dom.commonTags = document.getElementById('commonTagsList');
+    dom.bulkSuggestionsList = document.getElementById('bulkSuggestionsList');
+    dom.bulkSuggestionsHint = document.getElementById('bulkSuggestionsHint');
 
     if (!dom.selectBtn || !dom.panel) return;
 
@@ -124,6 +126,7 @@
     updateAllOrderBadges();
     updateCount();
     loadCommonTags();
+    loadBulkSuggestions();
     dispatchSelectionChanged();
   }
 
@@ -137,6 +140,7 @@
     });
     updateCount();
     updateCommonTagsDisplay();
+    clearBulkSuggestions();
     dispatchSelectionChanged();
   }
 
@@ -288,6 +292,133 @@
     });
   }
 
+  // ---------------------------
+  // Bulk ML suggestions (consensus across selection)
+  // ---------------------------
+  const BULK_SUGGESTIONS_MIN = 2;
+  const BULK_SUGGESTIONS_THRESHOLD = 0.8;
+  const BULK_SUGGESTIONS_CATEGORY_ORDER = ['character', 'copyright', 'general'];
+  const BULK_SUGGESTIONS_CATEGORY_LABEL = {
+    character: 'Characters',
+    copyright: 'Fandoms',
+    general:   'General',
+  };
+
+  function clearBulkSuggestions() {
+    if (dom.bulkSuggestionsList) dom.bulkSuggestionsList.innerHTML = '';
+    setBulkSuggestionsHint('Select 2+ images to see consensus suggestions.');
+  }
+
+  function setBulkSuggestionsHint(text, visible = true) {
+    if (!dom.bulkSuggestionsHint) return;
+    dom.bulkSuggestionsHint.textContent = text;
+    dom.bulkSuggestionsHint.style.display = visible ? '' : 'none';
+  }
+
+  async function loadBulkSuggestions() {
+    if (!dom.bulkSuggestionsList) return;
+    const ids = Array.from(state.selectedIds);
+    if (ids.length < BULK_SUGGESTIONS_MIN) {
+      clearBulkSuggestions();
+      return;
+    }
+
+    setBulkSuggestionsHint('Loading…');
+    dom.bulkSuggestionsList.innerHTML = '';
+
+    try {
+      const r = await fetch('/api/suggestions/bulk', {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({ image_ids: ids, threshold: BULK_SUGGESTIONS_THRESHOLD }),
+      });
+      const j = await r.json();
+      if (!j.ok) {
+        setBulkSuggestionsHint('Could not load suggestions.');
+        return;
+      }
+      renderBulkSuggestions(j.suggestions || {}, ids.length);
+    } catch (e) {
+      setBulkSuggestionsHint('Could not load suggestions.');
+    }
+  }
+
+  function renderBulkSuggestions(grouped, selectionSize) {
+    if (!dom.bulkSuggestionsList) return;
+    dom.bulkSuggestionsList.innerHTML = '';
+
+    let total = 0;
+    for (const cat of BULK_SUGGESTIONS_CATEGORY_ORDER) {
+      const items = (grouped && grouped[cat]) || [];
+      if (items.length === 0) continue;
+      total += items.length;
+
+      const group = document.createElement('div');
+      group.className = 'suggestions-category';
+      group.dataset.category = cat;
+
+      const label = document.createElement('div');
+      label.className = 'suggestions-category-label';
+      label.textContent = BULK_SUGGESTIONS_CATEGORY_LABEL[cat] || cat;
+      group.appendChild(label);
+
+      const chips = document.createElement('div');
+      chips.className = 'suggestions-chips';
+      for (const item of items) {
+        chips.appendChild(buildBulkSuggestionChip(item, selectionSize));
+      }
+      group.appendChild(chips);
+      dom.bulkSuggestionsList.appendChild(group);
+    }
+
+    if (total === 0) {
+      setBulkSuggestionsHint('No consensus suggestions for this selection.');
+    } else {
+      setBulkSuggestionsHint('', false);
+    }
+  }
+
+  function buildBulkSuggestionChip(item, selectionSize) {
+    const chip = document.createElement('div');
+    chip.className = 'suggestion-chip suggestion-chip-bulk';
+    chip.dataset.tagName = item.name;
+    chip.dataset.category = item.category;
+    const pct = Math.round((item.confidence || 0) * 100);
+    const covered = item.covered_count != null ? item.covered_count : selectionSize;
+    chip.title = `${item.name} — suggested for ${covered}/${selectionSize}`;
+
+    chip.innerHTML = `
+      <button type="button" class="sugg-btn sugg-accept" aria-label="Add to all selected">✓</button>
+      <span class="sugg-body">
+        <span class="sugg-label">${escapeHtml(item.name)}</span>
+        <span class="sugg-confidence">${pct}% · ${covered}/${selectionSize}</span>
+      </span>
+    `;
+
+    const acceptBtn = chip.querySelector('.sugg-accept');
+    if (acceptBtn) {
+      acceptBtn.addEventListener('click', () => acceptBulkSuggestion(chip));
+    }
+    return chip;
+  }
+
+  async function acceptBulkSuggestion(chip) {
+    if (chip.dataset.disabled === 'true') return;
+    chip.dataset.disabled = 'true';
+    chip.style.pointerEvents = 'none';
+    chip.style.opacity = '0.5';
+    const name = chip.dataset.tagName;
+    try {
+      await bulkAddTag(name);
+      chip.classList.add('leaving');
+      setTimeout(() => chip.remove(), 200);
+    } catch {
+      chip.dataset.disabled = 'false';
+      chip.style.pointerEvents = '';
+      chip.style.opacity = '';
+    }
+  }
+
   async function handleBulkAddTag(e) {
     e.preventDefault();
     const name = dom.tagInput.value.trim();