fix(files): list a hotel booking's files and files pinned to a stop on the place card

A hotel booking reaches its place through the stay, not its own place_id, so
the card listed the booking but not its confirmation. Links to a stop, which
MCP's link_trip_file and plugins can make, were never returned by the file
list at all; it now carries linked_assignment_ids. Without files the row no
longer opens to nothing.

shared/src/file/file.schema.ts

@@ -76,6 +76,7 @@ export type TripFile = z.infer<typeof tripFileSchema>;
 export const tripFileListItemSchema = tripFileSchema.extend({
   linked_reservation_ids: z.array(z.number()),
   linked_place_ids: z.array(z.number()),
+  linked_assignment_ids: z.array(z.number()),
   linked_budget_item_ids: z.array(z.number()),
 });
 export type TripFileListItem = z.infer<typeof tripFileListItemSchema>;