fix(downloads): apply original-filename toggle to individual downloads too (#507)

Follow-up to #498. The toggle reached zip downloads but single-photo
downloads still landed on disk with the renamed `event_individual_NNN.jpg`
even when the admin had flipped the setting on. Two reasons, fixed
in lockstep:

- Frontend overrode the server's Content-Disposition with a hardcoded
  `<a download="X">` attribute (`gallery.service.ts`, `photos.service.ts`)
  where X was the sanitized `photo.filename` known to the client. So
  the backend's correctly-formed `Content-Disposition` never reached
  the disk write. Added `parseContentDispositionFilename` (RFC 5987 +
  plain `filename=` fallback) and let the server name win when present.
- `secureImages.js` (enhanced/maximum protection's secure-download
  route) was missed in #498 and still emitted a hardcoded
  `filename="${photo.filename}"` regardless of the toggle. Wired it
  through `getUseOriginalFilenames` + `buildContentDisposition` so it
  matches the regular gallery download path.

Also exposed `Content-Disposition` via CORS so split (cross-origin)
frontend deployments can still read it from JavaScript. Same-origin
Docker deploys already had access; this is a defensive addition for
the split case.

frontend/src/services/gallery.service.ts

@@ -1,6 +1,7 @@
 import { api } from '../config/api';
 import type { GalleryInfo, GalleryData, GalleryStats, ResolvedGalleryIdentifier } from '../types';
 import { normalizeRequirePassword } from '../utils/accessControl';
+import { parseContentDispositionFilename } from '../utils/contentDisposition';
 
 export const galleryService = {
   // Verify share token
@@ -49,35 +50,38 @@ export const galleryService = {
 
   // Download single photo
   async downloadPhoto(slug: string, photoId: number, filename: string): Promise<void> {
-    try {
-      const response = await api.get(`/gallery/${slug}/download/${photoId}`, {
-        responseType: 'blob',
-      });
+    // Honour the server's Content-Disposition filename so the #493
+    // "use original camera filename" toggle reaches disk for single
+    // downloads (it already worked for zips because those skip the
+    // `<a download>` attribute). Falls back to the caller-provided
+    // sanitized filename if the header is unreadable.
+    const downloadFromResponse = (response: { data: Blob; headers: Record<string, string> }) => {
+      const headerName =
+        response.headers['content-disposition'] || response.headers['Content-Disposition'];
+      const serverFilename = parseContentDispositionFilename(headerName);
       const url = window.URL.createObjectURL(new Blob([response.data]));
       const link = document.createElement('a');
       link.href = url;
-      link.setAttribute('download', filename);
+      link.setAttribute('download', serverFilename || filename);
       document.body.appendChild(link);
       link.click();
       link.remove();
       window.URL.revokeObjectURL(url);
-    } catch (err) {
-      // Fallback: use the view endpoint if direct download fails (e.g., missing original)
-      try {
-        const response = await api.get(`/gallery/${slug}/photo/${photoId}`, {
-          responseType: 'blob',
-        });
-        const url = window.URL.createObjectURL(new Blob([response.data]));
-        const link = document.createElement('a');
-        link.href = url;
-        link.setAttribute('download', filename);
-        document.body.appendChild(link);
-        link.click();
-        link.remove();
-        window.URL.revokeObjectURL(url);
-      } catch (fallbackErr) {
-        throw fallbackErr;
-      }
+    };
+
+    try {
+      const response = await api.get(`/gallery/${slug}/download/${photoId}`, {
+        responseType: 'blob',
+      });
+      downloadFromResponse(response);
+    } catch {
+      // Fallback: use the view endpoint if direct download fails (e.g., missing original).
+      // The view endpoint doesn't emit a download-oriented Content-Disposition,
+      // so we expect the caller-supplied filename to win here.
+      const response = await api.get(`/gallery/${slug}/photo/${photoId}`, {
+        responseType: 'blob',
+      });
+      downloadFromResponse(response);
     }
   },
 

frontend/src/services/photos.service.ts

@@ -1,4 +1,5 @@
 import { api } from '../config/api';
+import { parseContentDispositionFilename } from '../utils/contentDisposition';
 
 export interface AdminPhoto {
   id: number;
@@ -102,11 +103,18 @@ class PhotosService {
     const response = await api.get(`/admin/events/${eventId}/photos/${photoId}/download`, {
       responseType: 'blob'
     });
-    
+
+    // Read the filename from the server's Content-Disposition so the
+    // #493 original-filename toggle reaches disk for admin downloads
+    // too (see contentDisposition.ts).
+    const headerName =
+      response.headers['content-disposition'] || response.headers['Content-Disposition'];
+    const serverFilename = parseContentDispositionFilename(headerName);
+
     const url = window.URL.createObjectURL(new Blob([response.data]));
     const link = document.createElement('a');
     link.href = url;
-    link.download = filename;
+    link.download = serverFilename || filename;
     document.body.appendChild(link);
     link.click();
     document.body.removeChild(link);