fix: drop migration backup-gate (FC-3h supersedes) + modal Escape via document-level listener so video focus can't swallow it

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/components/modal/ImageViewer.vue

@@ -2,9 +2,6 @@
   <Teleport to="body">
     <div
       class="fc-viewer" role="dialog" aria-modal="true"
-      @keydown.esc="$emit('close')"
-      @keydown.left="onArrowLeft"
-      @keydown.right="onArrowRight"
       tabindex="-1" ref="rootEl"
     >
       <button class="fc-viewer__close" @click="$emit('close')" aria-label="Close">
@@ -68,7 +65,7 @@ import VideoCanvas from './VideoCanvas.vue'
 import TagPanel from './TagPanel.vue'
 import ProvenancePanel from './ProvenancePanel.vue'
 
-defineEmits(['close'])
+const emit = defineEmits(['close'])
 
 const modal = useModalStore()
 const rootEl = ref(null)
@@ -86,14 +83,39 @@ const integrityBadge = computed(() => {
 })
 
 let prevBodyOverflow = null
+
+// Document-level keyboard handler. Bound on document (not on the modal
+// root) because <video> elements capture focus when the user interacts
+// with their controls — when video has focus, Escape and arrow keys
+// don't bubble reliably to ancestors. Listening on document side-steps
+// that. Filtered via isTextEntry so tag/comment inputs still get their
+// own keystrokes.
+function onKeyDown(ev) {
+  if (ev.key === 'Escape') {
+    if (isTextEntry(ev.target)) return
+    ev.preventDefault()
+    emit('close')
+  } else if (ev.key === 'ArrowLeft') {
+    if (isTextEntry(ev.target)) return
+    ev.preventDefault()
+    modal.goPrev()
+  } else if (ev.key === 'ArrowRight') {
+    if (isTextEntry(ev.target)) return
+    ev.preventDefault()
+    modal.goNext()
+  }
+}
+
 onMounted(async () => {
   prevBodyOverflow = document.body.style.overflow
   document.body.style.overflow = 'hidden'
+  document.addEventListener('keydown', onKeyDown, true)
   await nextFrame()
   rootEl.value?.focus()
 })
 onUnmounted(() => {
   document.body.style.overflow = prevBodyOverflow
+  document.removeEventListener('keydown', onKeyDown, true)
 })
 
 watch(() => modal.currentImageId, async () => {
@@ -105,16 +127,6 @@ function nextFrame() {
   return new Promise(resolve => requestAnimationFrame(resolve))
 }
 
-function onArrowLeft(ev) {
-  if (isTextEntry(ev.target)) return
-  ev.preventDefault()
-  modal.goPrev()
-}
-function onArrowRight(ev) {
-  if (isTextEntry(ev.target)) return
-  ev.preventDefault()
-  modal.goNext()
-}
 function isTextEntry(el) {
   if (!el) return false
   const tag = el.tagName