feat(gallery): reveal tiles on image load + single initial fetch

The 5×10 metadata batching only staggered the cheap layer (JSON);
thumbnails load as independent <img> requests and clustered, so tiles
"popped in together" after a wait. Two changes:

- GalleryItem reveals each tile when ITS OWN thumbnail fires @load (with
  an onMounted complete-check for cached thumbs), playing a showcase-style
  flip-up entrance. Tiles now cascade in natural load order instead of all
  at once. Honors prefers-reduced-motion.
- gallery store does ONE initial fetch (limit=50) instead of 10 serial
  /scroll round-trips. Fewer RTTs, faster first paint; the reveal-on-load
  is what makes appearance progressive now. Infinite scroll pulls 25/trigger.

Tests: GalleryItem gains is-loaded only after @load; loadInitial issues
exactly one scroll request at the initial limit.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/components/gallery/GalleryItem.vue

@@ -9,11 +9,16 @@
   >
     <div class="fc-gallery-item__media">
       <img
-        v-if="!isVideo" :src="image.thumbnail_url" :alt="`Image ${image.id}`"
-        loading="lazy" @error="onThumbError"
+        v-if="!isVideo" ref="imgEl" :src="image.thumbnail_url"
+        :alt="`Image ${image.id}`" loading="lazy"
+        :class="{ 'is-loaded': loaded }"
+        @load="loaded = true" @error="onThumbError"
       >
       <div v-else class="fc-gallery-item__video-thumb">
-        <img :src="image.thumbnail_url" :alt="`Video ${image.id}`" loading="lazy">
+        <img
+          ref="imgEl" :src="image.thumbnail_url" :alt="`Video ${image.id}`"
+          loading="lazy" :class="{ 'is-loaded': loaded }" @load="loaded = true"
+        >
         <v-icon class="fc-gallery-item__video-badge" icon="mdi-play-circle" />
       </div>
       <div v-if="thumbError" class="fc-gallery-item__placeholder">
@@ -38,7 +43,7 @@
 </template>
 
 <script setup>
-import { computed, ref } from 'vue'
+import { computed, onMounted, ref } from 'vue'
 import { useGallerySelectionStore } from '../../stores/gallerySelection.js'
 
 const props = defineProps({ image: { type: Object, required: true } })
@@ -46,6 +51,18 @@ const emit = defineEmits(['open'])
 
 const sel = useGallerySelectionStore()
 const thumbError = ref(false)
+
+// Reveal each tile when ITS OWN thumbnail finishes loading (`@load`), not
+// when its metadata batch lands — so tiles fade/flip in individually in
+// load order instead of popping in together (operator-flagged 2026-06-04).
+const loaded = ref(false)
+const imgEl = ref(null)
+onMounted(() => {
+  // A cached thumbnail can already be complete before @load binds; reflect
+  // that so the tile reveals instead of sitting invisible at opacity 0.
+  const el = imgEl.value
+  if (el && el.complete && el.naturalWidth > 0) loaded.value = true
+})
 const isVideo = computed(
   () => props.image.mime && props.image.mime.startsWith('video/')
 )
@@ -82,6 +99,30 @@ function onThumbError() { thumbError.value = true }
 }
 .fc-gallery-item__media img {
   width: 100%; height: 100%; object-fit: cover; display: block;
+  opacity: 0;
+}
+/* Entrance: each thumbnail flips up out of a slight backward tilt and
+   settles into place, played WHEN ITS OWN image finishes loading (the
+   `is-loaded` class) rather than on a batch/timer — so tiles cascade in
+   natural load order instead of popping in together. Mirrors the showcase
+   MasonryGrid entrance styling (operator-flagged 2026-06-04). */
+.fc-gallery-item__media img.is-loaded {
+  animation: fc-gallery-item-in 0.5s cubic-bezier(0.34, 1.45, 0.64, 1) both;
+}
+@keyframes fc-gallery-item-in {
+  0% {
+    opacity: 0;
+    transform: perspective(1000px) rotateX(-22deg) translateY(20px) scale(0.96);
+  }
+  55% { opacity: 1; }
+  100% {
+    opacity: 1;
+    transform: perspective(1000px) rotateX(0) translateY(0) scale(1);
+  }
+}
+@media (prefers-reduced-motion: reduce) {
+  .fc-gallery-item__media img { opacity: 1; }
+  .fc-gallery-item__media img.is-loaded { animation: none; }
 }
 .fc-gallery-item__video-thumb { position: relative; height: 100%; }
 .fc-gallery-item__video-badge {

frontend/src/stores/gallery.js

@@ -3,12 +3,15 @@ import { ref, computed } from 'vue'
 import { useApi } from '../composables/useApi.js'
 import { useInflightToken } from '../composables/useInflightToken.js'
 
-// Operator-confirmed 2026-05-30: fetch PAGE-sized chunks instead of one
-// 50-item request so items render as each batch lands. Total initial
-// count is unchanged (PAGE * INITIAL_BATCHES = 50). Infinite-scroll also
-// pulls PAGE per trigger to keep appends progressive.
-const PAGE = 5
-const INITIAL_BATCHES = 10
+// Initial paint is a SINGLE request (INITIAL_LIMIT). The old 10×serial-
+// batch loop (2026-05-30) only staggered METADATA, which isn't the visual
+// bottleneck — thumbnails load as independent `<img>` requests, and
+// GalleryItem now reveals each tile on its own image `@load`. One fetch is
+// far fewer round-trips and faster to first paint; the reveal-on-load is
+// what makes appearance progressive. Infinite scroll pulls PAGE per trigger.
+// Reworked 2026-06-04.
+const PAGE = 25
+const INITIAL_LIMIT = 50
 
 export const useGalleryStore = defineStore('gallery', () => {
   const api = useApi()
@@ -32,22 +35,16 @@ export const useGalleryStore = defineStore('gallery', () => {
     images.value = []
     dateGroups.value = []
     nextCursor.value = null
-    // Sequentially fetch INITIAL_BATCHES chunks so items render as each
-    // batch lands rather than blocking on one big response. Stop early
-    // when the backend reports no more pages.
-    for (let i = 0; i < INITIAL_BATCHES; i++) {
-      if (i > 0 && nextCursor.value === null) break
-      await loadMore()
-    }
+    await loadMore(INITIAL_LIMIT)
   }
 
-  async function loadMore() {
+  async function loadMore(limit = PAGE) {
     if (loading.value) return
     loading.value = true
     error.value = null
     const t = inflight.claim()
     try {
-      const params = { limit: PAGE, ...activeFilterParam() }
+      const params = { limit, ...activeFilterParam() }
       if (nextCursor.value) params.cursor = nextCursor.value
       const body = await api.get('/api/gallery/scroll', { params })
       if (!t.isCurrent()) return

frontend/test/components/galleryItem.spec.js

@@ -0,0 +1,28 @@
+// @vitest-environment happy-dom
+import { describe, it, expect } from 'vitest'
+
+import GalleryItem from '../../src/components/gallery/GalleryItem.vue'
+import { freshPinia, mountComponent } from '../support/mountComponent.js'
+
+describe('GalleryItem', () => {
+  const image = {
+    id: 7, sha256: 'a'.repeat(64), mime: 'image/jpeg',
+    width: 100, height: 100,
+    thumbnail_url: '/images/thumbs/aa/abc.jpg', artist: null,
+  }
+
+  it('reveals the thumbnail only once it has loaded, so tiles fade in individually', async () => {
+    const pinia = freshPinia()
+    const w = mountComponent(GalleryItem, { props: { image }, pinia })
+    const img = w.find('img')
+    expect(img.exists()).toBe(true)
+
+    // Pre-load: the tile must NOT be revealed, so it can fade in when its
+    // own thumbnail lands rather than pop together with its API batch.
+    expect(img.classes()).not.toContain('is-loaded')
+
+    await img.trigger('load')
+
+    expect(img.classes()).toContain('is-loaded')
+  })
+})

frontend/test/gallery.spec.js

@@ -49,4 +49,19 @@ describe('gallery store: tag/post filter exclusivity', () => {
     expect(scrollCall).toContain('post_id=7')
     expect(scrollCall).not.toContain('tag_id=')
   })
+
+  it('loadInitial issues exactly one scroll request at the initial limit', async () => {
+    const s = useGalleryStore()
+    const urls = []
+    // Non-null cursor: the old 10×serial-batch loop would have fired ten
+    // requests here. The single-fetch path must fire exactly one.
+    stubFetch((url) => {
+      urls.push(url)
+      return { status: 200, body: { images: [], date_groups: [], next_cursor: 'c1' } }
+    })
+    await s.loadInitial()
+    const scrollCalls = urls.filter(u => u.includes('/api/gallery/scroll'))
+    expect(scrollCalls).toHaveLength(1)
+    expect(scrollCalls[0]).toContain('limit=50')
+  })
 })