UI icons overhaul

I'd suggest to add more icons to the UI to tell buttons faster apart.
It could probably also be useful to create higher quality icons in the future (32x32 or higher resolution), because the current icon set under `chunky/src/res/icons` looks very pixelated for modern applications and might not always represent what they are used for.
While this is not a high priority, we could also look into including icon sets/icon fonts (like e.g. FontAwesome) to get a coherent design including common functions like "open folder/file", "save", "export", ...

Review the existing assets under chunky/src/res/icons and the single issue comment to understand the current icon set and proposed directions. Before implementation, clarify whether the goal is more icons, higher-resolution replacements, an icon set or font, or a combination; done cannot be determined until the scope and acceptance criteria are chosen.

Written by the indexing model from the issue text.