Thanks for the report 
Maybe you can add create a PR with trim last `/` on `basePath` ?
theme uri invalid with extra "/"
### Expected Behavior

Access /ui/flows get all extra resources.

### Actual Behaviour

Can't get theme-light.js and theme-light.css, here is actual URI, Please note there is an extra "/" after ui/

```
<link rel="stylesheet" href="/ui//css/theme-light.00305fce.css" data-theme="theme-light">
```
https://github.com/kestra-io/kestra/blob/0886e50d7fd828bafbea67e268f95665bd59616e/ui/public/index.html#L23-L26

https://github.com/kestra-io/kestra/blob/d9f02017a5f23b6581ca1b35d96392351a45a93f/ui/src/App.vue#L96-L110

Might be the culprit.


### Steps To Reproduce

1. Install istio and using oauth2-proxy for authentication.

### Environment Information

- Kestra Version: 0.5.0-BETA


### Example flow

_No response_
ui/src/App.vue
ui/src/App.vue
diff --git a/ui/src/App.vue b/ui/src/App.vue
index 0b233b5993..ec676de08e 100644
--- a/ui/src/App.vue
+++ b/ui/src/App.vue
@@ -98,11 +98,11 @@
                                 if (r.endsWith(".js")) {
                                     elem = document.createElement("script");
                                     elem.setAttribute("type", "text/javascript");
-                                    elem.setAttribute("src", basePath + "/" + r);
+                                    elem.setAttribute("src", basePath + r);
                                 } else {
                                     elem = document.createElement("link");
                                     elem.setAttribute("rel", "stylesheet");
-                                    elem.setAttribute("href", basePath + "/" + r);
+                                    elem.setAttribute("href", basePath + r);
                                 }
 
                                 elem.setAttribute("data-theme", theme);
