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/showcase.js

@@ -20,6 +20,15 @@
   let columnHeights = [];
   let isLoading = false;
   let currentColumnCount = 0;
+  const seenImageIds = new Set();
+
+  function buildRandomUrl(count) {
+    const params = new URLSearchParams({ count: String(count) });
+    if (seenImageIds.size > 0) {
+      params.set('exclude', [...seenImageIds].join(','));
+    }
+    return `/api/random-images?${params.toString()}`;
+  }
 
   // Initialize
   function init() {
@@ -149,6 +158,13 @@
     const imgEl = document.createElement('img');
     imgEl.src = img.thumb_url;
     imgEl.alt = img.filename;
+    // Reserve the correct layout slot before the image loads so the masonry
+    // doesn't reflow when thumbnails arrive. Width/height populate on import
+    // and may be missing on older records — fall back to natural sizing.
+    if (img.width && img.height) {
+      imgEl.width = img.width;
+      imgEl.height = img.height;
+    }
     if (useLazyLoading) {
       imgEl.loading = 'lazy';
     }
@@ -173,7 +189,10 @@
   }
 
   function distributeImages(images, useLazyLoading = false, animate = false) {
+    const colWidth = columns[0] ? columns[0].clientWidth : 0;
+
     images.forEach((img, i) => {
+      seenImageIds.add(img.id);
       const colIndex = getShortestColumnIndex();
       const item = createImageElement(img, useLazyLoading);
 
@@ -186,7 +205,13 @@
       }
 
       columns[colIndex].appendChild(item);
-      columnHeights[colIndex] += 300;
+      // Predict rendered height from the intrinsic aspect ratio so masonry
+      // packing is accurate before the thumb loads. Fall back to a flat guess
+      // when W/H are missing.
+      const predictedHeight = (colWidth && img.width && img.height)
+        ? colWidth * (img.height / img.width)
+        : 300;
+      columnHeights[colIndex] += predictedHeight;
       const imgEl = item.querySelector('img');
       imgEl.onload = () => { updateColumnHeights(); };
     });
@@ -228,10 +253,18 @@
     container.classList.add('loading');
 
     try {
-      const response = await fetch(`/api/random-images?count=20`);
+      let response = await fetch(buildRandomUrl(20));
       if (!response.ok) throw new Error('Failed to fetch');
+      let data = await response.json();
 
-      const data = await response.json();
+      // If the collection is exhausted for this session, reset and retry once
+      // so shuffle keeps feeling fresh on a "second lap".
+      if (data.images.length === 0 && seenImageIds.size > 0) {
+        seenImageIds.clear();
+        response = await fetch(buildRandomUrl(20));
+        if (!response.ok) throw new Error('Failed to fetch');
+        data = await response.json();
+      }
 
       // Clear everything
       columns.forEach(col => col.innerHTML = '');
@@ -254,7 +287,7 @@
     isLoading = true;
 
     try {
-      const response = await fetch(`/api/random-images?count=${LOAD_BATCH_SIZE}`);
+      const response = await fetch(buildRandomUrl(LOAD_BATCH_SIZE));
       if (!response.ok) throw new Error('Failed to fetch');
 
       const data = await response.json();