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/users/[username]/route.ts

@@ -8,6 +8,7 @@
 import { eq } from "drizzle-orm";
 import { apiJson } from "@/lib/api";
 import { db, User } from "@/lib/db";
+import { apiCacheKey, cacheSafe, redisCache } from "@/lib/redis-cache";
 
 export async function GET(
 	_req: Request,
@@ -16,33 +17,45 @@ export async function GET(
 	const { username } = await params;
 
 	try {
-		const [user] = await db
-			.select({
-				username: User.username,
-				look: User.look,
-				motto: User.motto,
-				rank: User.rank,
-				credits: User.credits,
-				online: User.online,
-				accountCreated: User.accountCreated,
-			})
-			.from(User)
-			.where(eq(User.username, username))
-			.limit(1);
+		const user = await redisCache(
+			apiCacheKey(`users:${username}`),
+			30,
+			async () => {
+				const [row] = await db
+					.select({
+						username: User.username,
+						look: User.look,
+						motto: User.motto,
+						rank: User.rank,
+						credits: User.credits,
+						online: User.online,
+						accountCreated: User.accountCreated,
+					})
+					.from(User)
+					.where(eq(User.username, username))
+					.limit(1);
+
+				if (!row) {
+					return null;
+				}
+
+				return cacheSafe({
+					username: row.username,
+					look: row.look,
+					motto: row.motto,
+					rank: row.rank,
+					credits: row.credits,
+					online: row.online === "1",
+					accountCreated: row.accountCreated,
+				});
+			},
+		);
 
 		if (!user) {
 			return apiJson({ error: "User not found" }, { status: 404 });
 		}
 
-		return apiJson({
-			username: user.username,
-			look: user.look,
-			motto: user.motto,
-			rank: user.rank,
-			credits: user.credits,
-			online: user.online === "1",
-			accountCreated: user.accountCreated,
-		});
+		return apiJson(user);
 	} catch {
 		// DB unreachable — behave as "not found" rather than 500.
 		return apiJson({ error: "User not found" }, { status: 404 });