gui: Favicon not working in Firefox bookmarks #9506
Description
What happened?
Firefox doesn't show any favicon at all when adding a bookmark to the Syncthing GUI, even with the static favicon introduced by #8850. It looks like Firefox prefers the last favicon that is found in <head> which is the link to favicon-{{syncthingStatus()}}.png. Because that file is not available on initial page load, it is not considered for bookmarks. The favicon logic for Firefox can be found here.
Switching the order of the favicon links in <head> fixes the behavior for Firefox while breaking the dynamic favicon for Chromium-based browsers.
A proper fix for this issue was suggested by @ajshea in #7638 (comment).
Syncthing version
v1.27.6
Platform & operating system
Linux x86
Browser version
Firefox 124.0.2
Relevant log output
No response