fix: back-merge v3.1.4 hotfixes into dev (#1371)

Port the three main-only fixes onto dev's (post-rewrite) architecture:
- fix(backups): prevent recursion when the backup path sits inside the backed-up dir
- fix(share): convert budget items to the viewer's base currency instead of a flat EUR
- fix(files): surface the descriptive server error for unsupported upload types (#1363)

Cherry-picked from 819aa793 on main; the SharedTripPage and useTripPlanner
conflicts were resolved to keep dev's font-scaling and full import set while
taking the fixes' currency conversion and translateApiError wiring.

client/src/components/Files/useFileManager.ts

@@ -1,7 +1,7 @@
 import { useState, useCallback, useEffect } from 'react'
 import { useDropzone } from 'react-dropzone'
 import { useToast } from '../shared/Toast'
-import { useTranslation } from '../../i18n'
+import { useTranslation, translateApiError } from '../../i18n'
 import { filesApi } from '../../api/client'
 import type { Place, Reservation, TripFile, Day, AssignmentsMap } from '../../types'
 import { useCanDo } from '../../store/permissionsStore'
@@ -119,8 +119,8 @@ export function useFileManager({ files = [], onUpload, onDelete, onUpdate, place
       if (lastId && (places.length > 0 || reservations.length > 0)) {
         setAssignFileId(lastId)
       }
-    } catch {
-      toast.error(t('files.uploadError'))
+    } catch (err) {
+      toast.error(translateApiError(t, err, 'files.uploadError'))
     } finally {
       setUploading(false)
     }

client/src/components/Planner/PlaceInspector.tsx

@@ -14,7 +14,7 @@ import { useAddonStore } from '../../store/addonStore'
 import { useSaveToCollectionStore } from '../../store/saveToCollectionStore'
 import { getCategoryIcon } from '../shared/categoryIcons'
 import { useToast } from '../shared/Toast'
-import { useTranslation } from '../../i18n'
+import { useTranslation, translateApiError } from '../../i18n'
 import type { Place, Category, Day, Assignment, Reservation, TripFile, AssignmentsMap } from '../../types'
 import type { CollectionStatus } from '@trek/shared'
 import { splitReservationDateTime, formatTime } from '../../utils/formatters'
@@ -255,7 +255,7 @@ export default function PlaceInspector({
       setFilesExpanded(true)
     } catch (err: unknown) {
       console.error('Upload failed', err)
-      toast.error(t('files.uploadError'))
+      toast.error(translateApiError(t, err, 'files.uploadError'))
     } finally {
       setIsUploading(false)
       if (fileInputRef.current) fileInputRef.current.value = ''