feat: safe deletion, album/asset delete, trash, README update

- volume-aware deletion: read-only volumes remove DB only, writable
  volumes soft-delete to trash with configurable grace period
- trash page with restore, worker purge sweep (TRASH_RETENTION_DAYS)
- album delete endpoint + sidebar trash icon
- asset delete from timeline selection toolbar
- all listing queries exclude trashed assets (deleted_at IS NULL)
- timeline ordered by EXIF capture date, date-summary endpoint
- README rewritten with features, setup, full env var table

k-photos-frontend/components/album-sidebar.tsx

@@ -14,11 +14,12 @@ import {
 import { Button } from "@/components/ui/button"
 import { Input } from "@/components/ui/input"
 import { useAlbums } from "@/hooks/use-albums"
-import { ImageIcon, PlusIcon } from "lucide-react"
+import { toast } from "sonner"
+import { ImageIcon, PlusIcon, Trash2Icon } from "lucide-react"
 
 export function AlbumSidebar() {
   const pathname = usePathname()
-  const { albums, createAlbum } = useAlbums()
+  const { albums, createAlbum, deleteAlbum } = useAlbums()
   const [isCreating, setIsCreating] = useState(false)
   const [newTitle, setNewTitle] = useState("")
 
@@ -59,14 +60,31 @@ export function AlbumSidebar() {
         )}
         <SidebarMenu>
           {albums.map((album) => (
-            <SidebarMenuItem key={album.id}>
+            <SidebarMenuItem key={album.id} className="group/album">
               <SidebarMenuButton
                 asChild
                 isActive={pathname === `/albums/${album.id}`}
               >
                 <Link href={`/albums/${album.id}`}>
                   <ImageIcon className="h-4 w-4" />
-                  <span>{album.title}</span>
+                  <span className="flex-1">{album.title}</span>
+                  <Button
+                    variant="ghost"
+                    size="icon"
+                    className="h-5 w-5 opacity-0 group-hover/album:opacity-100"
+                    onClick={async (e) => {
+                      e.preventDefault()
+                      e.stopPropagation()
+                      try {
+                        await deleteAlbum(album.id)
+                        toast.success("Album deleted")
+                      } catch {
+                        toast.error("Failed to delete album")
+                      }
+                    }}
+                  >
+                    <Trash2Icon className="h-3 w-3" />
+                  </Button>
                 </Link>
               </SidebarMenuButton>
             </SidebarMenuItem>