api+admin: let the curator take a photo off the landing, not just move it

Uploads still land in the community strip with consent on, by the uploader's own
tick — that default stays. What was missing is the curator's removal: the slot
select only offered the other three live placements, so "off the strip" meant
publishing the photo somewhere else or deleting the uploader's row.

`off` is a fifth slot value. The reel draws slot === 'strip' and each live slot
draws its own, so an `off` photo renders nowhere on the landing, while its owner
still has it in MY PHOTOS.

docker/backend/src/db.ts

@@ -83,8 +83,11 @@ CREATE INDEX IF NOT EXISTS idx_events_at ON events(at);
 
 // Where a curated photo is allowed to appear on the landing page: the community
 // strip, the live tester's preview, the creator lab's preview, or the QR card.
-// One is picked at random out of its slot on every page load.
-export const PHOTO_SLOTS = ['strip', 'tester', 'creator', 'qr'] as const;
+// One is picked at random out of its slot on every page load. `off` is the
+// curator's "take it off the landing, keep the row" — the reel and the three
+// live slots all draw by exact slot, so an `off` photo shows up nowhere, while
+// its owner still has it in MY PHOTOS.
+export const PHOTO_SLOTS = ['strip', 'tester', 'creator', 'qr', 'off'] as const;
 export type PhotoSlot = (typeof PHOTO_SLOTS)[number];
 export const isPhotoSlot = (v: unknown): v is PhotoSlot =>
   typeof v === 'string' && (PHOTO_SLOTS as readonly string[]).includes(v);