fix(ui): stronger frosted glass + frosted settings backdrop; declutter header

- Increase .glass blur (32px) so overlay menus (account) read as proper frosted glass.
- Blur the settings modal backdrop (overlay backdrop-blur) so the panel reliably
  frosts the content behind it instead of showing a sharp video through.
- Remove the now-redundant header buttons (dark/light, color scheme, grid/list) —
  they live in Settings → Appearance. Header keeps search, sync, bell, account.

frontend/src/App.tsx

@@ -132,12 +132,8 @@ export default function App() {
     <div className="h-screen flex flex-col bg-bg text-fg">
       <Header
         me={meQuery.data!}
-        theme={theme}
-        setTheme={setTheme}
         filters={filters}
         setFilters={setFilters}
-        view={view}
-        setView={changeView}
         page={page}
         setPage={setPage}
         onOpenSettings={() => setSettingsOpen(true)}