feat(files,memories): add gallery navigation to image lightboxes

Files lightbox: prev/next buttons, keyboard arrows, swipe on mobile,
thumbnail strip, file counter. Navigates between all images in the
current filtered view.

Memories lightbox: prev/next buttons, keyboard arrows, swipe on mobile,
photo counter. Navigates between all visible trip photos.

client/src/components/Files/FileManager.tsx

@@ -1,7 +1,7 @@
 import ReactDOM from 'react-dom'
 import { useState, useCallback, useRef, useEffect } from 'react'
 import { useDropzone } from 'react-dropzone'
-import { Upload, Trash2, ExternalLink, X, FileText, FileImage, File, MapPin, Ticket, StickyNote, Star, RotateCcw, Pencil, Check } from 'lucide-react'
+import { Upload, Trash2, ExternalLink, X, FileText, FileImage, File, MapPin, Ticket, StickyNote, Star, RotateCcw, Pencil, Check, ChevronLeft, ChevronRight } from 'lucide-react'
 import { useToast } from '../shared/Toast'
 import { useTranslation } from '../../i18n'
 import { filesApi } from '../../api/client'
@@ -37,49 +37,120 @@ function formatDateWithLocale(dateStr, locale) {
   } catch { return '' }
 }
 
-// Image lightbox
+// Image lightbox with gallery navigation
 interface ImageLightboxProps {
-  file: TripFile & { url: string }
+  files: (TripFile & { url: string })[]
+  initialIndex: number
   onClose: () => void
 }
 
-function ImageLightbox({ file, onClose }: ImageLightboxProps) {
+function ImageLightbox({ files, initialIndex, onClose }: ImageLightboxProps) {
   const { t } = useTranslation()
+  const [index, setIndex] = useState(initialIndex)
   const [imgSrc, setImgSrc] = useState('')
+  const [touchStart, setTouchStart] = useState<number | null>(null)
+  const file = files[index]
+
   useEffect(() => {
-    getAuthUrl(file.url, 'download').then(setImgSrc)
-  }, [file.url])
+    setImgSrc('')
+    if (file) getAuthUrl(file.url, 'download').then(setImgSrc)
+  }, [file?.url])
+
+  const goPrev = () => setIndex(i => Math.max(0, i - 1))
+  const goNext = () => setIndex(i => Math.min(files.length - 1, i + 1))
+
+  useEffect(() => {
+    const handler = (e: KeyboardEvent) => {
+      if (e.key === 'Escape') onClose()
+      if (e.key === 'ArrowLeft') goPrev()
+      if (e.key === 'ArrowRight') goNext()
+    }
+    window.addEventListener('keydown', handler)
+    return () => window.removeEventListener('keydown', handler)
+  }, [])
+
+  if (!file) return null
+
+  const hasPrev = index > 0
+  const hasNext = index < files.length - 1
+  const navBtn = (side: 'left' | 'right', onClick: () => void, show: boolean): React.ReactNode => show ? (
+    <button onClick={e => { e.stopPropagation(); onClick() }}
+      style={{
+        position: 'absolute', top: '50%', [side]: 12, transform: 'translateY(-50%)', zIndex: 10,
+        background: 'rgba(0,0,0,0.5)', border: 'none', borderRadius: '50%', width: 40, height: 40,
+        display: 'flex', alignItems: 'center', justifyContent: 'center', cursor: 'pointer',
+        color: 'rgba(255,255,255,0.8)', transition: 'background 0.15s',
+      }}
+      onMouseEnter={e => (e.currentTarget.style.background = 'rgba(0,0,0,0.75)')}
+      onMouseLeave={e => (e.currentTarget.style.background = 'rgba(0,0,0,0.5)')}>
+      {side === 'left' ? <ChevronLeft size={22} /> : <ChevronRight size={22} />}
+    </button>
+  ) : null
+
   return (
     <div
-      style={{ position: 'fixed', inset: 0, background: 'rgba(0,0,0,0.88)', zIndex: 2000, display: 'flex', alignItems: 'center', justifyContent: 'center' }}
+      style={{ position: 'fixed', inset: 0, background: 'rgba(0,0,0,0.92)', zIndex: 2000, display: 'flex', flexDirection: 'column' }}
       onClick={onClose}
+      onTouchStart={e => setTouchStart(e.touches[0].clientX)}
+      onTouchEnd={e => {
+        if (touchStart === null) return
+        const diff = e.changedTouches[0].clientX - touchStart
+        if (diff > 60) goPrev()
+        else if (diff < -60) goNext()
+        setTouchStart(null)
+      }}
     >
-      <div style={{ position: 'relative', maxWidth: '90vw', maxHeight: '90vh' }} onClick={e => e.stopPropagation()}>
-        <img
-          src={imgSrc}
-          alt={file.original_name}
-          style={{ maxWidth: '90vw', maxHeight: '90vh', objectFit: 'contain', borderRadius: 8, display: 'block' }}
-        />
-        <div style={{ position: 'absolute', top: -40, left: 0, right: 0, display: 'flex', alignItems: 'center', justifyContent: 'space-between', padding: '0 4px' }}>
-          <span style={{ fontSize: 12, color: 'rgba(255,255,255,0.7)', overflow: 'hidden', textOverflow: 'ellipsis', whiteSpace: 'nowrap', maxWidth: '80%' }}>{file.original_name}</span>
-          <div style={{ display: 'flex', gap: 8 }}>
-            <button
-              onClick={async () => { const u = await getAuthUrl(file.url, 'download'); window.open(u, '_blank', 'noreferrer') }}
-              style={{ background: 'none', border: 'none', cursor: 'pointer', color: 'rgba(255,255,255,0.7)', display: 'flex', padding: 0 }}
-              title={t('files.openTab')}
-            >
-              <ExternalLink size={16} />
-            </button>
-            <button onClick={onClose} style={{ background: 'none', border: 'none', cursor: 'pointer', color: 'rgba(255,255,255,0.7)', display: 'flex', padding: 0 }}>
-              <X size={18} />
-            </button>
-          </div>
+      {/* Header */}
+      <div style={{ display: 'flex', alignItems: 'center', justifyContent: 'space-between', padding: '10px 16px', flexShrink: 0 }} onClick={e => e.stopPropagation()}>
+        <span style={{ fontSize: 12, color: 'rgba(255,255,255,0.7)', overflow: 'hidden', textOverflow: 'ellipsis', whiteSpace: 'nowrap', flex: 1 }}>
+          {file.original_name}
+          <span style={{ marginLeft: 8, color: 'rgba(255,255,255,0.4)' }}>{index + 1} / {files.length}</span>
+        </span>
+        <div style={{ display: 'flex', gap: 8, flexShrink: 0 }}>
+          <button
+            onClick={async () => { const u = await getAuthUrl(file.url, 'download'); window.open(u, '_blank', 'noreferrer') }}
+            style={{ background: 'none', border: 'none', cursor: 'pointer', color: 'rgba(255,255,255,0.7)', display: 'flex', padding: 4 }}
+            title={t('files.openTab')}>
+            <ExternalLink size={16} />
+          </button>
+          <button onClick={onClose} style={{ background: 'none', border: 'none', cursor: 'pointer', color: 'rgba(255,255,255,0.7)', display: 'flex', padding: 4 }}>
+            <X size={18} />
+          </button>
         </div>
       </div>
+
+      {/* Main image + nav */}
+      <div style={{ flex: 1, display: 'flex', alignItems: 'center', justifyContent: 'center', position: 'relative', minHeight: 0 }} onClick={e => e.stopPropagation()}>
+        {navBtn('left', goPrev, hasPrev)}
+        {imgSrc && <img src={imgSrc} alt={file.original_name} style={{ maxWidth: '85vw', maxHeight: '80vh', objectFit: 'contain', borderRadius: 8, display: 'block' }} />}
+        {navBtn('right', goNext, hasNext)}
+      </div>
+
+      {/* Thumbnail strip */}
+      {files.length > 1 && (
+        <div style={{ display: 'flex', gap: 4, justifyContent: 'center', padding: '10px 16px', flexShrink: 0, overflowX: 'auto' }} onClick={e => e.stopPropagation()}>
+          {files.map((f, i) => (
+            <ThumbImg key={f.id} file={f} active={i === index} onClick={() => setIndex(i)} />
+          ))}
+        </div>
+      )}
     </div>
   )
 }
 
+function ThumbImg({ file, active, onClick }: { file: TripFile & { url: string }; active: boolean; onClick: () => void }) {
+  const [src, setSrc] = useState('')
+  useEffect(() => { getAuthUrl(file.url, 'download').then(setSrc) }, [file.url])
+  return (
+    <button onClick={onClick} style={{
+      width: 48, height: 48, borderRadius: 6, overflow: 'hidden', border: active ? '2px solid #fff' : '2px solid transparent',
+      opacity: active ? 1 : 0.5, cursor: 'pointer', padding: 0, background: '#111', flexShrink: 0, transition: 'opacity 0.15s',
+    }}>
+      {src && <img src={src} alt="" style={{ width: '100%', height: '100%', objectFit: 'cover', display: 'block' }} />}
+    </button>
+  )
+}
+
 // Authenticated image — fetches a short-lived download token and renders the image
 function AuthedImg({ src, style }: { src: string; style?: React.CSSProperties }) {
   const [authSrc, setAuthSrc] = useState('')
@@ -169,7 +240,7 @@ interface FileManagerProps {
 export default function FileManager({ files = [], onUpload, onDelete, onUpdate, places, days = [], assignments = {}, reservations = [], tripId, allowedFileTypes }: FileManagerProps) {
   const [uploading, setUploading] = useState(false)
   const [filterType, setFilterType] = useState('all')
-  const [lightboxFile, setLightboxFile] = useState(null)
+  const [lightboxIndex, setLightboxIndex] = useState<number | null>(null)
   const [showTrash, setShowTrash] = useState(false)
   const [trashFiles, setTrashFiles] = useState<TripFile[]>([])
   const [loadingTrash, setLoadingTrash] = useState(false)
@@ -324,9 +395,12 @@ export default function FileManager({ files = [], onUpload, onDelete, onUpdate,
     }
   }
 
+  const imageFiles = filteredFiles.filter(f => isImage(f.mime_type))
+
   const openFile = (file) => {
     if (isImage(file.mime_type)) {
-      setLightboxFile(file)
+      const idx = imageFiles.findIndex(f => f.id === file.id)
+      setLightboxIndex(idx >= 0 ? idx : 0)
     } else {
       setPreviewFile(file)
     }
@@ -453,7 +527,7 @@ export default function FileManager({ files = [], onUpload, onDelete, onUpdate,
   return (
     <div className="flex flex-col h-full" style={{ fontFamily: "-apple-system, BlinkMacSystemFont, 'SF Pro Text', system-ui, sans-serif" }} onPaste={handlePaste} tabIndex={-1}>
       {/* Lightbox */}
-      {lightboxFile && <ImageLightbox file={lightboxFile} onClose={() => setLightboxFile(null)} />}
+      {lightboxIndex !== null && <ImageLightbox files={imageFiles} initialIndex={lightboxIndex} onClose={() => setLightboxIndex(null)} />}
 
       {/* Assign modal */}
       {assignFileId && ReactDOM.createPortal(