fix(voice): proper shadcn select dropdowns + top reactors leaderboard

- ui/select: trigger default w-full h-9 (was w-fit h-8 — selects rendered
  tiny/misaligned); callers keep size override via className
- VoiceConnectionCard: labeled full-width h-10 selects (Server/Guild +
  Voice Channel), guild icon + name in options, channel type icon +
  'no akses' tag, empty states, htmlFor/id a11y wiring
- GuildSelector sidebar + messages channel filter bumped to match
- Backend GET /api/dashboard/reactors: top users by net reactions given
  (adds-removes) + messages_reacted + emojis_used
- Reactions tab: second 'Top reaktor' leaderboard panel

services/frontend/src/app/(dashboard)/messages/page.tsx

@@ -135,7 +135,7 @@ export default function MessagesPage() {
             value={selectedChannel}
             onValueChange={(v) => setSelectedChannel(v ?? "")}
           >
-            <SelectTrigger className="h-8 w-40 glass border-glass-border text-xs">
+            <SelectTrigger className="h-9 w-48">
               <SelectValue placeholder="All channels" />
             </SelectTrigger>
             <SelectContent>