feat: use of nerdfont symbols.

[jckirton]

Problem

I feel that concord could look a bit better if it used nerdfont symbols for things like the server folder icon. It could also allow for some additional functionality (for example, mobile/desktop online indicator).

Proposed solution

Have a setting that toggles if nerdfont symbols are used.

Some proposed symbols:

• Guild folder (closed): nf-fa-folder (\uf07b)
• Guild folder (open): nf-fa-folder_open (\uf07c)
• Online (mobile): nf-fa-mobile_phone (\uf10b)

Alternatives considered

No response

Additional context

No response

Confirmations

• I searched existing issues and discussions for the same idea.
• This request does not involve self-bot automation, mass actions, or scraping.