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.

server/src/nest/files/files.controller.ts

@@ -39,7 +39,8 @@ const UPLOAD = {
   fileFilter: (_req: unknown, file: Express.Multer.File, cb: (err: Error | null, accept: boolean) => void) => {
     const ext = path.extname(file.originalname).toLowerCase();
     const reject = () => {
-      const err: Error & { statusCode?: number } = new Error('File type not allowed');
+      // i18n key — the client resolves it via t() (see translateApiError).
+      const err: Error & { statusCode?: number } = new Error('files.uploadErrorType');
       err.statusCode = 400;
       cb(err, false);
     };

server/src/services/backupService.ts

@@ -184,9 +184,21 @@ export async function createBackup(): Promise<BackupInfo> {
         // Exclude the place-photo and trek-memory caches: both are re-derivable
         // (re-fetched on demand, keyed on stable ids) and would otherwise dominate
         // backup size. Restores self-heal — the cache dirs are recreated at startup.
+        //
+        // Also exclude backups/ and restore-*/: these live under data/, not uploads/,
+        // but when an install maps data and uploads to the SAME directory (a
+        // misconfiguration, but a catastrophic one) the glob would otherwise sweep
+        // every prior backup zip into the new archive — each run embedding all
+        // previous runs, so size compounds without bound (see issue #1358). Ignoring
+        // them keeps the backup bounded regardless of how the volumes are mounted.
         archive.glob(
           '**/*',
-          { cwd: uploadsDir, ignore: ['photos/google/**', 'photos/trek/**'], nodir: true, dot: true },
+          {
+            cwd: uploadsDir,
+            ignore: ['photos/google/**', 'photos/trek/**', 'backups/**', 'restore-*/**'],
+            nodir: true,
+            dot: true,
+          },
           { prefix: 'uploads' },
         );
       }

server/src/services/shareService.ts

@@ -2,6 +2,7 @@ import { db, canAccessTrip } from '../db/database';
 import crypto from 'crypto';
 import { loadTagsByPlaceIds } from './queryHelpers';
 import { serveFilePath } from './placePhotoCache';
+import { getUserSettings } from './settingsService';
 
 const PLACE_PHOTO_PROXY_PREFIX = '/api/maps/place-photo/';
 
@@ -219,8 +220,23 @@ export function getSharedTripData(token: string): Record<string, any> | null {
     ? db.prepare('SELECT m.*, u.username, u.avatar FROM collab_messages m JOIN users u ON m.user_id = u.id WHERE m.trip_id = ? AND m.deleted = 0 ORDER BY m.created_at').all(tripId)
     : [];
 
+  // Display currency the share owner sees in their Costs view. A public viewer has
+  // no logged-in user, so the owner's per-user `default_currency` (with the admin
+  // instance default already merged in by getUserSettings) is embedded in the
+  // payload and used by the client to convert every expense — otherwise guests
+  // fall back to the trip's base currency and see the wrong totals (#1361).
+  // getUserSettings merges admin defaults under the user's own settings, so this
+  // honours per-user → admin-default; we then fall back to trip currency → EUR.
+  let baseCurrency = (trip as { currency?: string }).currency || 'EUR';
+  if (shareRow.created_by != null) {
+    const ownerDefault = getUserSettings(shareRow.created_by)['default_currency'];
+    if (typeof ownerDefault === 'string' && ownerDefault.trim()) {
+      baseCurrency = ownerDefault.trim();
+    }
+  }
+
   return {
-    trip, days, assignments, dayNotes, places, categories, permissions,
+    trip, baseCurrency, days, assignments, dayNotes, places, categories, permissions,
     reservations: permissions.share_bookings ? reservations : [],
     accommodations: permissions.share_bookings ? accommodations : [],
     packing: permissions.share_packing ? packing : [],