Returning an empty `icon_name` in `tray_linux_ksni.rs` forces SNI
panels (e.g., KDE Plasma) to render the explicit `IconPixmap` data.
This prevents panels from incorrectly resolving the full-color app icon
from the system theme instead of the intended monochrome tray glyph.
Also updates `src-tauri/icons/icon-symbolic.svg` and regenerates
all `tray-dark-*.png` and `tray-light-*.png` assets.
Adds `static/logo.svg` as the main application logo.
