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/photo-grid.tsx

@@ -8,7 +8,7 @@ import { ImageViewer } from "./image-viewer"
 import { AddToAlbumDialog } from "./add-to-album-dialog"
 import { Button } from "@/components/ui/button"
 import { Spinner } from "@/components/ui/spinner"
-import { ImagePlusIcon, XIcon, CheckSquareIcon } from "lucide-react"
+import { ImagePlusIcon, XIcon, CheckSquareIcon, Trash2Icon } from "lucide-react"
 
 interface PhotoGridProps {
   groups: DateGroup[]
@@ -16,6 +16,7 @@ interface PhotoGridProps {
   hasMore: boolean
   onLoadMore: () => void
   onRemoveAsset?: (assetId: string) => void
+  onDeleteAssets?: (assetIds: string[]) => void
 }
 
 export function PhotoGrid({
@@ -24,6 +25,7 @@ export function PhotoGrid({
   hasMore,
   onLoadMore,
   onRemoveAsset,
+  onDeleteAssets,
 }: PhotoGridProps) {
   const sentinelRef = useRef<HTMLDivElement>(null)
   const [selectedIndex, setSelectedIndex] = useState<number | null>(null)
@@ -94,13 +96,26 @@ export function PhotoGrid({
           {onRemoveAsset && selectedIds.size > 0 && (
             <Button
               size="sm"
-              variant="destructive"
+              variant="secondary"
               onClick={() => {
                 selectedIds.forEach((id) => onRemoveAsset(id))
                 exitSelection()
               }}
             >
-              Remove
+              Remove from Album
+            </Button>
+          )}
+          {onDeleteAssets && selectedIds.size > 0 && (
+            <Button
+              size="sm"
+              variant="destructive"
+              onClick={() => {
+                onDeleteAssets(Array.from(selectedIds))
+                exitSelection()
+              }}
+            >
+              <Trash2Icon className="mr-1.5 h-3.5 w-3.5" />
+              Delete
             </Button>
           )}
           <Button size="sm" variant="ghost" onClick={exitSelection}>