Add performance optimizations and component refactors

- Cache read-heavy public API routes via redisCache (leaderboard, values,
  shop, articles, photos, guilds, teams, staff, users, home, radio, badges)
- Add single-flight and bounded-memory cache layer with unit tests
- Parallelize independent DB queries on search, rares, shop, staff, polls
  and profile pages
- Push radio points leaderboard aggregation to SQL with a LIMIT
- Split studio-client and import-furni-client into focused modules
- Clean up next.config.ts

src/app/api/leaderboard/route.ts

@@ -1,6 +1,7 @@
 import { desc, eq, inArray } from "drizzle-orm";
 import { apiJson } from "@/lib/api";
 import { db, User, UsersCurrency } from "@/lib/db";
+import { apiCacheKey, redisCache } from "@/lib/redis-cache";
 
 // Public REST API — leaderboard. Mirrors src/app/leaderboard/page.tsx.
 // AtomCMS-faithful currency type ids (see UsersCurrency):
@@ -75,11 +76,15 @@ export async function GET(req: Request) {
 				? requested
 				: "credits";
 
-		const rows =
-			type === "credits"
-				? await loadCreditsRows()
-				: // eslint-disable-next-line security/detect-object-injection -- type validated to "diamonds"|"duckets"
-					await loadCurrencyRows(CURRENCY_TYPE[type]);
+		const rows = await redisCache(
+			apiCacheKey(`leaderboard:${type}`),
+			60,
+			async () =>
+				type === "credits"
+					? await loadCreditsRows()
+					: // eslint-disable-next-line security/detect-object-injection -- type validated to "diamonds"|"duckets"
+						await loadCurrencyRows(CURRENCY_TYPE[type]),
+		);
 
 		return apiJson({ type, data: rows }, { status: 200 });
 	} catch {