fix(web): correct SVG MIME type from image/svg to image/svg+xml

Go's mime package doesn't register .svg with the correct type by default,
causing browsers to reject SVG resources when used with CSS mask-image.

Fixes #1410

web/backend/embed.go

@@ -4,6 +4,7 @@ import (
 	"embed"
 	"io/fs"
 	"log"
+	"mime"
 	"net/http"
 	"path"
 	"strings"
@@ -12,6 +13,12 @@ import (
 //go:embed all:dist
 var frontendFS embed.FS
 
+func init() {
+	// Register correct MIME type for SVG files
+	// Go's mime package doesn't register .svg with the correct type by default
+	mime.AddExtensionType(".svg", "image/svg+xml")
+}
+
 // registerEmbedRoutes sets up the HTTP handler to serve the embedded frontend files
 func registerEmbedRoutes(mux *http.ServeMux) {
 	// Attempt to get the subdirectory 'dist' where Vite usually builds