feat(glass): glassify modal inner panels, dropdowns & list rows (Phase 2)

Medium container surfaces -> the glass system so they refract the backdrop
consistently: Playlists row (bg-card->glass-card), DownloadCenter user-picker +
ShareDialog share-picker dropdowns (bg-card->glass-menu), DownloadCenter stat
cards / download rows / usage block, ShareDialog share-link block, VideoEditor
selection bar, ProfileEditor profile rows (bg-card/40|bg-surface/60->glass-card).
Tight admin rows and tiny inputs left solid on purpose.

frontend/src/components/ProfileEditor.tsx

@@ -97,7 +97,7 @@ export default function ProfileEditor({ onClose }: { onClose: () => void }) {
       <div className="space-y-1.5 mb-4">
         <div className="text-xs uppercase tracking-wide text-muted">{t("downloads.profiles.builtin")}</div>
         {builtins.map((p) => (
-          <div key={p.id} className="flex items-center gap-2 text-sm px-3 py-1.5 rounded-lg bg-surface/60">
+          <div key={p.id} className="flex items-center gap-2 text-sm px-3 py-1.5 rounded-lg glass-card">
             <Lock className="w-3.5 h-3.5 text-muted shrink-0" />
             <span className="flex-1 truncate">{p.name}</span>
           </div>
@@ -106,7 +106,7 @@ export default function ProfileEditor({ onClose }: { onClose: () => void }) {
           <div className="text-xs uppercase tracking-wide text-muted pt-2">{t("downloads.profiles.yours")}</div>
         )}
         {mine.map((p) => (
-          <div key={p.id} className="flex items-center gap-2 text-sm px-3 py-1.5 rounded-lg bg-surface/60">
+          <div key={p.id} className="flex items-center gap-2 text-sm px-3 py-1.5 rounded-lg glass-card">
             <span className="flex-1 truncate">{p.name}</span>
             <button onClick={() => startEdit(p)} title={t("downloads.actions.rename")} className="p-1 rounded hover:bg-surface text-muted hover:text-fg">
               <Pencil className="w-3.5 h-3.5" />