[Bug]: Default Nextcloud Icon appears when file sharing via link instead of custom favicon (embeds)

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• Nextcloud Server is running on 64bit capable CPU, PHP and OS.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

As above appears in all embeds whether sharing by discord, Whatsapp, Messenger, Facebook, Chrome and so on.

To confirm on the theming page all icons and logos have been set to my custom png image with a size of 32x32 and 256x256. In all other ways the logos/favicon appears as it should, but seems to have dissappeared with embeds since the latest NC edition 25.0.3.

Steps to reproduce

1. share a file via link.
2. logo appears when sent.

Expected behavior

custom favicon/logo should appear.

Installation method

None

Operating system

None

PHP engine version

None

Web server

None

Database engine version

None

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

No response

List of activated Apps

Enabled:
  - activity: 2.17.0
  - admin_audit: 1.15.0
  - announcementcenter: 6.5.0
  - bruteforcesettings: 2.5.0
  - calendar: 4.2.3
  - circles: 25.0.0
  - cloud_federation_api: 1.8.0
  - comments: 1.15.0
  - contacts: 5.0.3
  - contactsinteraction: 1.6.0
  - dashboard: 7.5.0
  - dav: 1.24.0
  - deck: 1.8.3
  - drawio: 2.1.0
  - encryption: 2.13.0
  - external: 5.0.2
  - federatedfilesharing: 1.15.0
  - federation: 1.15.0
  - files: 1.20.1
  - files_accesscontrol: 1.15.1
  - files_downloadactivity: 1.15.0
  - files_external: 1.17.0
  - files_pdfviewer: 2.6.0
  - files_rightclick: 1.4.0
  - files_sharing: 1.17.0
  - files_trackdownloads: 1.11.0
  - files_trashbin: 1.15.0
  - files_versions: 1.18.0
  - firstrunwizard: 2.14.0
  - groupfolders: 13.1.1
  - impersonate: 1.11.0
  - integration_github: 1.0.15
  - integration_google: 1.0.9
  - integration_whiteboard: 0.0.14
  - logreader: 2.10.0
  - lookup_server_connector: 1.13.0
  - maps: 0.2.4
  - money: 0.15.0
  - nextcloud_announcements: 1.14.0
  - notes: 4.6.0
  - notifications: 2.13.1
  - oauth2: 1.13.0
  - password_policy: 1.15.0
  - photos: 2.0.1
  - privacy: 1.9.0
  - provisioning_api: 1.15.0
  - quota_warning: 1.15.0
  - recommendations: 1.4.0
  - registration: 2.1.0
  - related_resources: 1.0.3
  - richdocuments: 7.1.1
  - richdocumentscode: 22.5.802
  - serverinfo: 1.15.0
  - settings: 1.7.0
  - sharebymail: 1.15.0
  - side_menu: 3.6.0
  - snowflakestheme: 1.0.0
  - spreed: 15.0.3
  - support: 1.8.0
  - survey_client: 1.13.0
  - systemtags: 1.15.0
  - tasks: 0.14.5
  - terms_of_service: 2.1.0
  - text: 3.6.0
  - theming: 2.0.1
  - theming_customcss: 1.12.0
  - twofactor_backupcodes: 1.14.0
  - twofactor_totp: 7.0.0
  - unsplash: 2.2.0
  - updatenotification: 1.15.0
  - user_status: 1.5.0
  - viewer: 1.9.0
  - weather_status: 1.5.0
  - welcome: 1.0.8
  - workflowengine: 2.7.0
Disabled:
  - analytics: 4.7.2
  - audioplayer: 3.3.1
  - breezedark: 25.0.0
  - carnet: 0.24.6
  - electronicsignatures: 2.0.3
  - end_to_end_encryption: 1.11.1
  - extract: 1.3.5
  - files_antivirus: 4.0.2
  - flow_notifications: 1.5.0
  - forms: 3.1.0
  - health: 1.6.1
  - jsloader: 1.5.0
  - phonetrack: 0.7.4
  - quicknotes: 0.8.5
  - radio: 1.0.3
  - socialsharing_email: 2.5.0
  - suspicious_login: 4.2.1
  - talk_matterbridge: 1.25.2
  - user_ldap
  - video_converter: 1.0.5

Nextcloud Signing status

No errors have been found.

Nextcloud Logs

No response

Additional info

No response

No files, tests, or entry points are named. Start by reproducing a file-link share with a customized Nextcloud favicon and inspect the metadata used by external embeds; done means the custom favicon appears instead of the default Nextcloud icon.