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/components/admin-sidebar.tsx

@@ -0,0 +1,57 @@
+"use client"
+
+import Link from "next/link"
+import { usePathname } from "next/navigation"
+import { useAuth } from "@/hooks/use-auth"
+import {
+  SidebarGroup,
+  SidebarGroupLabel,
+  SidebarGroupContent,
+  SidebarMenu,
+  SidebarMenuItem,
+  SidebarMenuButton,
+} from "@/components/ui/sidebar"
+import {
+  HardDriveIcon,
+  ListIcon,
+  PlugIcon,
+  WorkflowIcon,
+  FileTextIcon,
+  CopyIcon,
+} from "lucide-react"
+
+const ADMIN_LINKS = [
+  { href: "/admin/storage", label: "Storage", icon: HardDriveIcon },
+  { href: "/admin/jobs", label: "Jobs", icon: ListIcon },
+  { href: "/admin/plugins", label: "Plugins", icon: PlugIcon },
+  { href: "/admin/pipelines", label: "Pipelines", icon: WorkflowIcon },
+  { href: "/admin/sidecars", label: "Sidecars", icon: FileTextIcon },
+  { href: "/admin/duplicates", label: "Duplicates", icon: CopyIcon },
+]
+
+export function AdminSidebar() {
+  const { isAdmin } = useAuth()
+  const pathname = usePathname()
+
+  if (!isAdmin) return null
+
+  return (
+    <SidebarGroup>
+      <SidebarGroupLabel>Admin</SidebarGroupLabel>
+      <SidebarGroupContent>
+        <SidebarMenu>
+          {ADMIN_LINKS.map(({ href, label, icon: Icon }) => (
+            <SidebarMenuItem key={href}>
+              <SidebarMenuButton asChild isActive={pathname === href}>
+                <Link href={href}>
+                  <Icon className="h-4 w-4" />
+                  <span>{label}</span>
+                </Link>
+              </SidebarMenuButton>
+            </SidebarMenuItem>
+          ))}
+        </SidebarMenu>
+      </SidebarGroupContent>
+    </SidebarGroup>
+  )
+}