docs(feedback): say in the code why bitdex-image-feed survives its producer

The slug has no writer since the BitDex decommission, so it reads as leftover and
the obvious cleanup is to delete it. Deleting it breaks a read path: this enum is
what getFeedbackAreaSchema validates a moderator's area query against, so removing
the slug makes every historical row filed under it unqueryable through that route.

The reason existed only in a PR body and a mail thread, which is where intent goes
to be refactored away. Putting it at the constant so the next person meets it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KYrq2ighNp2rABTAvpzhj9

src/shared/constants/feedback.constants.ts

@@ -1,5 +1,11 @@
 // Plain strings, not a Prisma enum: adding an area costs a constant here and no
 // migration, and its Flipt flag is derived from the slug.
+//
+// 🔴 `bitdex-image-feed` has no producer — BitDex was decommissioned 2026-09-01 and
+// its prompt went with it. KEEP IT ANYWAY. This enum is what `getFeedbackAreaSchema`
+// validates a moderator's query against, so deleting the slug makes every historical
+// feedback row filed under it unreadable through that route. It cannot grow: nothing
+// writes it any more.
 export const FEEDBACK_AREAS = ['bitdex-image-feed', 'apps-marketplace'] as const;
 
 export type FeedbackArea = (typeof FEEDBACK_AREAS)[number];