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.

server/src/db/repositories/FileLinks.repository.ts

@@ -25,6 +25,7 @@ export interface FileLinkWithReservationRow extends FileLinkRow {
 export interface FileLinkTargetRow {
   file_id: number;
   reservation_id: number | null;
+  assignment_id: number | null;
   place_id: number | null;
   budget_item_id: number | null;
 }
@@ -64,7 +65,7 @@ export class FileLinksRepository extends TrekRepository<FileLinks> {
     if (file_ids.length === 0) return [];
     return await this.kysely<FileLinksKyselyDB>()
       .selectFrom('file_links')
-      .select(['file_id', 'reservation_id', 'place_id', 'budget_item_id'])
+      .select(['file_id', 'reservation_id', 'assignment_id', 'place_id', 'budget_item_id'])
       .where('file_id', 'in', file_ids)
       .execute();
   }

server/src/nest/files/files.service.ts

@@ -349,6 +349,8 @@ export class FilesService {
         ...formatFile(f),
         linked_reservation_ids: fileLinks.filter((l) => l.reservation_id).map((l) => l.reservation_id),
         linked_place_ids: fileLinks.filter((l) => l.place_id).map((l) => l.place_id),
+        // MCP's link_trip_file and plugins can pin a file to one stop of the plan.
+        linked_assignment_ids: fileLinks.filter((l) => l.assignment_id).map((l) => l.assignment_id),
         linked_budget_item_ids: fileLinks.filter((l) => l.budget_item_id).map((l) => l.budget_item_id),
       };
     });

server/src/nest/plugins/protocol/output-contract.ts

@@ -225,6 +225,7 @@ export const PLUGIN_ENTITY_CONTRACT = {
       'url',
       'linked_reservation_ids',
       'linked_place_ids',
+      'linked_assignment_ids',
       'linked_budget_item_ids',
     ],
   },