fix(ui): consolidate Orbit / Server / Live header dropdowns (#725)

* fix(ui): consolidate Orbit / Server / Live header dropdowns

The three header dropdown popovers each had their own container style.
Live used a glass utility class with backdrop-filter that read poorly on
many themes (reported by cucadmuh). Move all three onto the shared
`.nav-library-dropdown-panel` container — same bg, border, shadow and
radius via existing semantic tokens (`--bg-card`, `--border-dropdown`,
`--shadow-dropdown`, `--radius-md`). Item styles per dropdown stay
case-specific.

- NowPlayingDropdown: replace `glass animate-fade-in` with
  `nav-library-dropdown-panel animate-fade-in`; drop now-redundant inline
  borderRadius / boxShadow / zIndex; keep padding + gap for the
  user-list breathing room.
- OrbitStartTrigger: add `nav-library-dropdown-panel` alongside
  `orbit-launch-pop`. The component-local class is now reduced to the
  menu-specific min-width + tighter item gap; bg / border / shadow /
  radius / padding inherit from the shared container.
- Drop the unused `.glass` utility class; no other call sites.

* docs(changelog): header dropdown consistency fix (#725)

src/components/OrbitStartTrigger.tsx

@@ -82,7 +82,7 @@ export default function OrbitStartTrigger() {
       </button>
 
       {popoverOpen && createPortal(
-        <div ref={popRef} className="orbit-launch-pop" style={popoverStyle} role="menu">
+        <div ref={popRef} className="nav-library-dropdown-panel orbit-launch-pop" style={popoverStyle} role="menu">
           <button type="button" className="orbit-launch-pop__item" onClick={pickCreate}>
             <Plus size={14} />
             <span>{t('orbit.launchCreate')}</span>