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/backend/src/modules/dashboard/dashboard.routes.ts

@@ -97,5 +97,15 @@ export function createDashboardRouter(): Router {
     }),
   );
 
+  // GET /api/dashboard/reactors — top users by reactions given
+  router.get(
+    "/dashboard/reactors",
+    asyncHandler(async (req: Request, res: Response) => {
+      const limit = Number(req.query.limit) || 20;
+      const reactors = await dashboardService.getTopReactors(limit);
+      res.json(reactors);
+    }),
+  );
+
   return router;
 }