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/lib/services/site-settings.ts

@@ -29,6 +29,10 @@ const IS_PRERENDER =
 
 class SiteSettings {
 	private cache: { map: Map<string, string>; expiresAt: number } | null = null;
+	// Single-flight: one request (re)loads the map, the rest await it — the
+	// root layout reads settings on every render, so concurrent misses must
+	// not each hammer Redis/DB (cache-stampede protection).
+	private inFlight: Promise<Map<string, string>> | null = null;
 
 	private async loadFromDb(): Promise<Map<string, string>> {
 		try {
@@ -42,13 +46,7 @@ class SiteSettings {
 		}
 	}
 
-	private async load(): Promise<Map<string, string>> {
-		if (this.cache !== null) {
-			if (IS_PRERENDER || this.cache.expiresAt > Date.now()) {
-				return this.cache.map;
-			}
-		}
-
+	private async loadFromCacheOrDb(): Promise<Map<string, string>> {
 		if (redis) {
 			try {
 				const cached = await redis.get(REDIS_CACHE_KEY);
@@ -85,6 +83,22 @@ class SiteSettings {
 		return map;
 	}
 
+	private async load(): Promise<Map<string, string>> {
+		if (this.cache !== null) {
+			if (IS_PRERENDER || this.cache.expiresAt > Date.now()) {
+				return this.cache.map;
+			}
+		}
+
+		if (this.inFlight) return this.inFlight;
+
+		const run = this.loadFromCacheOrDb().finally(() => {
+			this.inFlight = null;
+		});
+		this.inFlight = run;
+		return run;
+	}
+
 	async getAll(): Promise<Map<string, string>> {
 		return await this.load();
 	}
@@ -127,6 +141,7 @@ class SiteSettings {
 
 	async reload(): Promise<void> {
 		this.cache = null;
+		this.inFlight = null;
 		if (redis) {
 			try {
 				await redis.del(REDIS_CACHE_KEY);