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/app/(app)/page.tsx

@@ -0,0 +1,35 @@
+"use client"
+
+import { useMemo } from "react"
+import { useTimeline, useDateSummary } from "@/hooks/use-timeline"
+import { groupByDate } from "@/lib/timeline"
+import { PhotoGrid } from "@/components/photo-grid"
+import { DateScrubber } from "@/components/date-scrubber"
+
+export default function TimelinePage() {
+  const { assets, isLoading, hasMore, loadMore, total } = useTimeline()
+  const { data: dateSummary } = useDateSummary()
+  const groups = useMemo(() => groupByDate(assets), [assets])
+
+  return (
+    <div className="flex flex-col gap-4">
+      <div className="flex items-center justify-between">
+        <h1 className="text-lg font-semibold">Timeline</h1>
+        {total > 0 && (
+          <span className="text-sm text-muted-foreground">
+            {total} photos
+          </span>
+        )}
+      </div>
+      <div className="flex gap-1">
+        <PhotoGrid
+          groups={groups}
+          isLoading={isLoading}
+          hasMore={hasMore}
+          onLoadMore={() => loadMore()}
+        />
+        <DateScrubber dates={dateSummary ?? []} />
+      </div>
+    </div>
+  )
+}