feat: frontend MVP — auth, timeline, upload, albums, admin, image viewer

Backend:
- user roles (DB + JWT + first-user-is-admin)
- volume-aware file resolver (multi-volume asset serving)
- directory scanner uses volume URI directly
- date-summary endpoint (capture date from EXIF)
- timeline ordered by capture date
- list endpoints: volumes, plugins, pipelines, library paths
- delete endpoints: volumes, library paths
- configurable upload body limit (MAX_UPLOAD_BYTES)

Frontend:
- auth: login/register, token refresh, role-based admin gate
- timeline: date-grouped grid, infinite scroll, date scrubber
- image viewer: fullscreen zoom/pan/pinch, metadata sidebar
- upload: drag-drop, sequential upload, progress tracking
- albums: create, add/remove photos, asset picker dialog
- admin: storage (import library), jobs (pagination, error details),
  plugins (list + toggle), pipelines, sidecars, duplicates
- multi-select mode with add-to-album action
- TanStack Query for all data fetching

k-photos-frontend/hooks/use-timeline.ts

@@ -0,0 +1,46 @@
+"use client"
+
+import { useInfiniteQuery, useQuery } from "@tanstack/react-query"
+import api from "@/lib/api"
+import type { TimelineResponse, DateSummaryResponse } from "@/lib/types"
+
+const PAGE_SIZE = 40
+
+export function useTimeline() {
+  const query = useInfiniteQuery({
+    queryKey: ["timeline"],
+    queryFn: async ({ pageParam = 0 }) => {
+      const { data } = await api.get<TimelineResponse>("/assets/timeline", {
+        params: { limit: PAGE_SIZE, offset: pageParam },
+      })
+      return data
+    },
+    initialPageParam: 0,
+    getNextPageParam: (lastPage, allPages) => {
+      const loaded = allPages.reduce((n, p) => n + p.assets.length, 0)
+      return loaded < lastPage.total ? loaded : undefined
+    },
+  })
+
+  const assets = query.data?.pages.flatMap((p) => p.assets) ?? []
+  const total = query.data?.pages[0]?.total ?? 0
+
+  return {
+    assets,
+    total,
+    isLoading: query.isLoading,
+    hasMore: query.hasNextPage,
+    loadMore: query.fetchNextPage,
+    isFetchingMore: query.isFetchingNextPage,
+  }
+}
+
+export function useDateSummary() {
+  return useQuery({
+    queryKey: ["date-summary"],
+    queryFn: async () => {
+      const { data } = await api.get<DateSummaryResponse>("/assets/date-summary")
+      return data.dates
+    },
+  })
+}