frontend: route all photo queries through sidecar timeline proxy

- listPhotos → /api/sidecar/timeline (was /photos)
- countPhotos → /api/sidecar/timeline (was /photos)
- hasPhotosMatching → /api/sidecar/timeline (was /photos)
- Sidecar handler forwards X-Count header for countPhotos()
- Sidecar adjusts X-Count to reflect post-filtered count

sidecar/handlers_photos.go

@@ -39,6 +39,10 @@ func handlePhotos(pp *ppClient) gin.HandlerFunc {
 
 		// If the user has no BasePath (admin/empty), return as-is.
 		if basePath == "" {
+			// Forward PhotoPrism's X-Count header for countPhotos().
+			if count := resp.Header.Get("X-Count"); count != "" {
+				c.Header("X-Count", count)
+			}
 			c.JSON(http.StatusOK, photos)
 			return
 		}
@@ -62,6 +66,8 @@ func handlePhotos(pp *ppClient) gin.HandlerFunc {
 			}
 		}
 
+		// Forward X-Count header adjusted to the filtered count.
+		c.Header("X-Count", itoa(len(filtered)))
 		c.JSON(http.StatusOK, filtered)
 	}
 }