[Bug]: NC33 visual bug: strong separation between files sidebar and content

### ⚠️ This issue respects the following points: ⚠️ - [x] This is a **bug**, not a question or a configuration/webserver/proxy issue. - [x] This issue is **not** already reported on [Github](https://github.com/nextcloud/server/issues?q=is%3Aopen+is%3Aissue+label%3Abug) OR [Nextcloud Community Forum](https://help.nextcloud.com/) _(I've searched it)_. - [x] Nextcloud Server **is** up to date. See [Maintenance and Release Schedule](https://github.com/nextcloud/server/wiki/Maintenance-and-Release-Schedule) for supported versions. - [x] I agree to follow Nextcloud's [Code of Conduct](https://nextcloud.com/contribute/code-of-conduct/). ### Bug description Hi, I recently switched over to NC33 and can't get my eyes out of this little graphical bug. <img width="554" height="136" alt="Image" src="https://github.com/user-attachments/assets/3b2ab6f9-2806-4326-a5b4-07e93bf71b53" /> As you can see, there is a strong separation between the sidebar and the files content. At first I thought a radius on the right side was missing, but looking at what has been done on NC34, I think this is more likely to be a missing background color around the content part. (Same page on NC34 below) <img width="554" height="136" alt="Image" src="https://github.com/user-attachments/assets/9f10c1b3-14f1-4996-b5ff-cd3117efd33f" /> This has been reproduced on multiple NC33 instances, none of which has either Custom CSS applied nor theming apps from the appstore. Current workaround: While I couldn't easily have the NC34 look using customCSS, I removed the radius of the file apps, making it look like other pages (settings for example) ```css #app-content-vue { border-radius: unset !important; } ``` Best regards, ### Steps to reproduce 1. Browse files ### Expected behavior Coherent styling ### Nextcloud Server version 33 ### Operating system _No response_ ### PHP engine version _No response_ ### Web server _No response_ ### Database engine version _No response_ ### Is this bug present after an update or on a fresh install? _No response_ ### Are you using the Nextcloud Server Encryption module? _No response_ ### What user-backends are you using? - [ ] Default user-backend _(database)_ - [ ] LDAP/ Active Directory - [ ] SSO - SAML - [ ] Other ### Configuration report ```json ``` ### List of activated Apps ```shell ``` ### Nextcloud Signing status ```shell ``` ### Nextcloud Logs ```json ``` ### Additional info _No response_