fix(journey): serve local file when uploading photos with Immich sync enabled

After upload, trek_photos.provider is immediately flipped to 'immich' even
though Immich's thumbnail generation is async. streamPhoto then routed to
Immich, which returned an error for the not-yet-processed asset. Because
Cache-Control was set before the proxy attempt, the error response was cached
by the browser for 24h — breaking thumbnails until a hard refresh bypassed
the cache and Immich had finished processing.

- streamPhoto now prefers the local file_path when it exists on disk,
  regardless of provider; Immich/Synology are only used when no local
  file is available (fixes the immediate broken-thumbnail symptom)
- pipeAsset sets Cache-Control: no-store on upstream errors and uses the
  caller-supplied default only on success (prevents cache poisoning)
- streamImmichAsset no longer pre-sets Cache-Control before the proxy
- streamSynologyAsset passes the same defaultCacheControl through pipeAsset

Closes #691

server/src/services/memories/photoResolverService.ts

@@ -69,15 +69,18 @@ export async function streamPhoto(
     return;
   }
 
+  if (photo.file_path) {
+    const localPath = path.join(__dirname, '../../../uploads', photo.file_path);
+    if (fs.existsSync(localPath)) {
+      res.set('Cache-Control', 'public, max-age=86400');
+      res.sendFile(localPath);
+      return;
+    }
+  }
+
   switch (photo.provider) {
     case 'local': {
-      const filePath = path.join(__dirname, '../../../uploads', photo.file_path!);
-      if (!fs.existsSync(filePath)) {
-        res.status(404).json({ error: 'File not found' });
-        return;
-      }
-      res.set('Cache-Control', 'public, max-age=86400');
-      res.sendFile(filePath);
+      res.status(404).json({ error: 'File not found' });
       return;
     }
     case 'immich': {