ui(duplicates): show parent folder + full-path tooltip on each thumbnail

Two copies of IMG_1234.jpg sitting in different folders looked
identical on the duplicates grid — same filename, same dimensions,
same Best heuristic. The user had no way to pick which copy to keep
without opening each in the preview overlay.

Backend: include filepath in the per-member payload from
GET /api/v1/library/duplicates/groups (was filename-only).

Frontend: a black 65% strip at the bottom of every duplicate
thumbnail showing the parent folder name (the actual discriminator
when filenames match), with the full filepath surfaced via the
native title tooltip on hover. The dimensions chip moves from
bottom-left to top-left so the bottom strip can run edge-to-edge.

memberToPhoto stops faking filepath=filename (a years-old workaround
that broke any code path needing the real path); the synthetic Photo
the grid hands to PhotoThumbnail now carries the real filepath.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/components/duplicates/DuplicatesView.tsx

@@ -450,19 +450,28 @@ const DuplicateGroupSection = memo(function DuplicateGroupSection({
                   Keep this
                 </button>
               )}
-              {/* Dimensions chip — bottom-LEFT. Neutral metadata variant
-               *  matches the family. Rare collision with a manual rating
-               *  (also bottom-left) is tolerated: rated duplicates are
-               *  uncommon in practice. */}
+              {/* Dimensions chip — top-LEFT (Best / Keep this lives
+               *  top-right; bottom is reserved for the path strip). */}
               <div
                 className={cn(
-                  'pointer-events-none absolute bottom-1 left-1 z-10 font-mono',
+                  'pointer-events-none absolute left-1.5 top-1.5 z-10 font-mono',
                   THUMB_BADGE_BASE,
                   THUMB_BADGE_NEUTRAL
                 )}
               >
                 {formatDimensions(member)}
               </div>
+              {/* Path strip — full-width across the bottom. Shows the
+               *  parent folder name (the actual discriminator when two
+               *  copies share the same filename), truncating from the
+               *  right if necessary. Full filepath surfaces via the
+               *  native tooltip on hover. */}
+              <div
+                className="pointer-events-none absolute bottom-0 left-0 right-0 z-10 truncate bg-black/65 px-1.5 py-0.5 text-[10px] text-white"
+                title={photoByMemberId.get(member.id)!.filepath}
+              >
+                {duplicatePathLabel(photoByMemberId.get(member.id)!.filepath)}
+              </div>
             </div>
           )
         })}
@@ -505,6 +514,23 @@ function formatBytes(n: number): string {
   return `${n}B`
 }
 
+/** Short label for the bottom path strip on a duplicate thumbnail.
+ *  Goal: tell two copies-with-the-same-filename apart at a glance, so
+ *  we want the parent folder name — that's almost always the
+ *  discriminator (different shoots, different years, different
+ *  upload sources). When the parent folder is unhelpful (e.g. the
+ *  filename is itself sitting at the root) we fall back to the file
+ *  basename. Long folder names get text-overflow-ellipsis'd by the
+ *  enclosing strip's `truncate`. */
+function duplicatePathLabel(filepath: string): string {
+  if (!filepath) return ''
+  const parts = filepath.split('/').filter(Boolean)
+  if (parts.length === 0) return filepath
+  if (parts.length === 1) return parts[0]
+  // The second-to-last segment IS the parent directory.
+  return parts[parts.length - 2]
+}
+
 /** Adapt a DuplicateGroupMember (the slim API shape) to a Photo, which
  *  is what PhotoThumbnail expects. We deliberately set is_duplicate=false
  *  on the synthetic Photo so the duplicate badge isn't drawn on every
@@ -512,7 +538,7 @@ function formatBytes(n: number): string {
 function memberToPhoto(m: DuplicateGroupMember): Photo {
   return {
     id: m.id,
-    filepath: m.filename, // good enough for the RAW/video extension regex
+    filepath: m.filepath,
     filename: m.filename,
     media_type: m.media_type,
     width: m.width,

frontend/src/services/api.ts

@@ -538,6 +538,10 @@ export const library = {
 export interface DuplicateGroupMember {
   id: string
   filename: string
+  /** Full path of the file on disk. Powers the path strip in the
+   *  Duplicates view so the user can tell two same-named-different-
+   *  folder copies apart at a glance. */
+  filepath: string
   taken_at: string | null
   file_size: number | null
   width: number | null