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/templates/gallery.html

@@ -144,6 +144,11 @@
     <p class="form-help">Common tags across selected images:</p>
     <div id="commonTagsList" class="tags"></div>
   </div>
+  <div class="bulk-editor-section">
+    <h4>Suggestions</h4>
+    <p class="form-help" id="bulkSuggestionsHint">Select 2+ images to see consensus suggestions.</p>
+    <div id="bulkSuggestionsList" class="suggestions-list"></div>
+  </div>
   {% if series_info %}
   <div class="bulk-editor-section bulk-editor-series">
     <h4>📚 Add to Series</h4>
@@ -179,91 +184,7 @@
 <script src="{{ url_for('static', filename='js/gallery-infinite.js') }}"></script>
 <script src="{{ url_for('static', filename='js/view-modal.js') }}"></script>
 <script src="{{ url_for('static', filename='js/bulk-select.js') }}"></script>
-
 {% if series_info %}
-<script>
-// Series Editor functionality (integrated into bulk editor panel)
-document.addEventListener('DOMContentLoaded', () => {
-  const startPageInput = document.getElementById('startPageInput');
-  const bulkAddToSeriesBtn = document.getElementById('bulkAddToSeriesBtn');
-  const feedbackEl = document.getElementById('seriesEditorFeedback');
-  const seriesTagId = {{ series_info.tag_id }};
-
-  // Update button state based on selection
-  function updateAddButtonState() {
-    const selectedCount = window.selectedImages ? window.selectedImages.size : 0;
-    bulkAddToSeriesBtn.disabled = selectedCount === 0;
-    bulkAddToSeriesBtn.textContent = selectedCount > 0
-      ? `Add ${selectedCount} to Series`
-      : 'Add to Series';
-  }
-
-  // Listen for selection changes
-  document.addEventListener('selectionChanged', updateAddButtonState);
-
-  // Add selected images to series
-  bulkAddToSeriesBtn.addEventListener('click', async () => {
-    if (!window.selectedImages || window.selectedImages.size === 0) return;
-
-    // Use selectionOrder (click order) for page ordering
-    const imageIds = window.selectionOrder ? [...window.selectionOrder] : Array.from(window.selectedImages);
-    const startPage = parseInt(startPageInput.value) || 1;
-
-    bulkAddToSeriesBtn.disabled = true;
-    bulkAddToSeriesBtn.textContent = 'Adding...';
-    feedbackEl.innerHTML = '';
-
-    try {
-      const r = await fetch(`/api/series/${seriesTagId}/pages/bulk-add`, {
-        method: 'POST',
-        headers: { 'Content-Type': 'application/json' },
-        body: JSON.stringify({ image_ids: imageIds, start_page: startPage })
-      });
-      const data = await r.json();
-
-      if (data.ok) {
-        let msg = `Added ${data.added.length} image(s) to series.`;
-        if (data.skipped.length > 0) {
-          msg += ` Skipped ${data.skipped.length}.`;
-        }
-        feedbackEl.innerHTML = `<div class="feedback-success">${msg}</div>`;
-
-        // Update the starting page input to the next available page
-        if (data.added.length > 0) {
-          const lastPage = data.added[data.added.length - 1].page_number;
-          startPageInput.value = lastPage + 1;
-        }
-
-        // Clear selection
-        if (window.clearSelection) {
-          window.clearSelection();
-        }
-
-        // Update page count in header
-        const pageCountEl = document.getElementById('seriesPageCount');
-        if (pageCountEl) {
-          const currentCount = parseInt(pageCountEl.textContent) || 0;
-          pageCountEl.textContent = `${currentCount + data.added.length} pages`;
-        }
-
-        // Show "Read Series" button if it was hidden (first pages added)
-        const readBtn = document.querySelector('.series-header-actions .primary-btn');
-        if (!readBtn && data.added.length > 0) {
-          location.reload(); // Simplest way to update the UI
-        }
-      } else {
-        feedbackEl.innerHTML = `<div class="feedback-error">${data.error}</div>`;
-      }
-    } catch (e) {
-      feedbackEl.innerHTML = `<div class="feedback-error">Error: ${e.message}</div>`;
-    } finally {
-      updateAddButtonState();
-    }
-  });
-
-  // Initial state
-  updateAddButtonState();
-});
-</script>
+<script src="{{ url_for('static', filename='js/gallery-series-editor.js') }}"></script>
 {% endif %}
 {% endblock %}