Small updates to "Public channels"

[ioeylim]

• Add the "P" icon to all public channels in the "Recent channels" sidebar
• Add the "P" icon to public channels in the profile page
• Add a mouseover text to the "P" icon
• Update the "P" icon with the 0 border radius icon
• The dropdown menu still says "Make channel public" even when it is a public channel #619

[0xTranqui]

completed #1 in this pr https://github.com/1ifeworld/river/pull/539