refactor: unify favicon for index.html and Electron

[KristjanESPERANTO]

In #3407 we already talked about unifying them.

• Create SVG favicon (better then png)
• Replace base64 placeholder in index.html with SVG favicon
• Update electron.js to use SVG favicon instead of mm2.png
• Add favicon.svg to server static routes
• Remove mm2.png

[sdetweil]

sorry, I don't remember conversation about this.. what problem does it solve?

[KristjanESPERANTO]

sorry, I don't remember conversation about this.

No problem. I see, you apparently didn't participate in the PR discussion.

what problem does it solve?

It doesn't really solve anything, it's just cleaner and more consistent.

[sdetweil]

it's just cleaner and more consistent.

as compared to what?

how does it help our users, our product and our team?
you mention electron, how about all the other browsers available? are there version restrictions?

I am not an active software developer, never have been. current trends also never interested me.
reliability, stability, supportability and maintainability have always been my focus.

i am against change for change sake.

[khassel]

I vote for this change.

• It's technical a more modern solution than the existing one
• it unifies the icons used in electron and server-only
• it replaces the ugly in server-only

[rejas]

I also vote for this change, modernizing stuff helps in the long term.