[client] Add light mode with system, light, and dark theme options (#7344)

* desktop UI light mode

* Theme review fixes plus macOS window outline fix

* Windows runtime chrome re-theming plus apply serialization

* Windows chrome threading and theme event ordering fixes

* Darken toggle and setting sidebar text

* resolve theme appearance, apply on UI thread

* read theme once per window

* Re-assert Windows dark opt-in after SetTheme

* split app-wide GTK theming from per-window chrome

* Update Wails dependency and checksums

* KDE tray icon panel fix

* Five review fixes: theme ordering, cgo dedup, KDE panel resolution

* Path guard hardening, toggle contrast, windows comment

* non-vacuous escape tests

* Default view edits

* Polish settings nav, controls, borders, and disc

* Profiles settings boarder, modals, and buttons

* Additional edits based on feedback

* Switch colors away from slight blue hue

* Update missing lang

* Fix vertical tab active view

client/ui/frontend/src/modules/main/MainHeader.tsx

@@ -74,7 +74,9 @@ export const MainHeader = () => {
                     <IconButton
                         icon={MoreVertical}
                         iconClassName={"text-nb-gray-200 wails-no-draggable"}
-                        className={"select-none"}
+                        className={
+                            "select-none hover:bg-nb-gray-800 data-[state=open]:bg-nb-gray-800 dark:hover:bg-nb-gray-900 dark:data-[state=open]:bg-nb-gray-900"
+                        }
                         aria-label={t("header.menu.open")}
                         aria-haspopup={"menu"}
                         aria-expanded={menuOpen}