fix(auth): keep secondary positions in permission checks

IAM lets an employee hold several positions, but the vendored JwtGuard
collapses employee.positions[] down to a single employee.position and
drops the rest. Non-delegate secondary positions vanished entirely, so
staff on two posts resolved to one post's permissions and every check
on the other rejected them.

FreightJwtGuard re-attaches the full list from the same session
snapshot the parent guard already read, so nothing extra is fetched
per request beyond a cached session lookup. employee.position is left
untouched, keeping audit logging and delegation unaffected.
collectPermissionKeys and collectPositionTypeKeys now union across
every position, and /me returns them all.

Verified against a real two-position user (djibouti-gl-director +
djibouti-gl-chief) on the local dev database:

  /me positions                     1   -> 2
  /me permissionKeys                17  -> 28
  GET /api/interchange-documents    403 -> 200
  GET /api/trains                   403 -> 200

11 permissions recovered, none lost. Six single-position users return
byte-identical payloads before and after.

apps/edr-freight-api/src/modules/exports/exports.controller.ts

@@ -3,7 +3,7 @@ import { ApiBearerAuth, ApiOperation, ApiTags } from '@nestjs/swagger';
 import { InjectDataSource } from '@nestjs/typeorm';
 import { DataSource } from 'typeorm';
 import { CurrentUser } from '@edr/api-common';
-import { JwtGuard } from '@tria-plc/api-common/modules/auth/services/jwt.guard';
+import { FreightJwtGuard } from '../../common/freight-jwt.guard';
 import type { Response } from 'express';
 import type { TCurrentUser } from '@tria-plc/api-common/modules/auth/types/current-user.type';
 
@@ -57,7 +57,7 @@ const toCatalogEntry = (dataset: ExportDataset): ExportCatalogEntry => ({
 @ApiTags('Exports')
 @ApiBearerAuth()
 @Controller('exports')
-@UseGuards(JwtGuard)
+@UseGuards(FreightJwtGuard)
 export class ExportsController {
   constructor(
     private readonly runner: ExportRunnerService,