desloppify: code health overhaul plus abuse hardening (140 green, strict 87.2)

Honest baseline after removing 45 gaming suppressions. Structural: lib/game plus root hooks extraction, CORS origin echo, DEV_ORIGINS layering. Fixes: error-cause binding, discord 5xx split, null-cache guard, co-located tests, rejecting-fetch coverage, naming and typing cleanup, socket controller, cache bound, cascade helpers, latch resets. Hardening: per-IP rate limit on API routes, deterministic-miss UX, retry cooldown plus cap. Suite 140 green, build plus lint clean.

lib/game/discord-app.ts

@@ -0,0 +1,95 @@
+import { warnDev } from "@/lib/log";
+
+export function discordAppIconUrl(
+    applicationId: string,
+    iconHash: string | null,
+    size = 128,
+): string | null {
+    if (!iconHash) {
+        return null;
+    }
+    const extension = iconHash.startsWith("a_") ? "gif" : "png";
+    return `https://cdn.discordapp.com/app-icons/${applicationId}/${iconHash}.${extension}?size=${size}`;
+}
+
+export function discordGameUrl(gameId: string): string {
+    return `https://discord.com/games/${gameId}`;
+}
+
+export function discordAppCoverUrl(
+    applicationId: string,
+    coverHash: string | null,
+    size = 512,
+): string | null {
+    if (!coverHash) {
+        return null;
+    }
+    return `https://cdn.discordapp.com/app-icons/${applicationId}/${coverHash}.png?size=${size}`;
+}
+
+export function steamdbAppUrl(steamId: string): string {
+    return `https://steamdb.info/app/${steamId}/`;
+}
+
+export interface DiscordAppInfo {
+    id: string;
+    name: string;
+    icon: string | null;
+    iconUrl: string | null;
+    coverImage: string | null;
+    coverUrl: string | null;
+    gameId: string;
+    gameUrl: string;
+}
+
+interface DiscordRpcResponse {
+    id?: string;
+    name?: string;
+    icon?: string | null;
+    cover_image?: string | null;
+    linked_games?: Array<{ id: string }> | null;
+}
+
+export async function getDiscordAppInfo(applicationId: string): Promise<DiscordAppInfo | null> {
+    if (!/^\d+$/.test(applicationId)) {
+        return null;
+    }
+    let response: Response;
+    try {
+        response = await fetch(`https://discord.com/api/v10/applications/${applicationId}/rpc`, {
+            headers: { "User-Agent": "fristy.net (personal site)" },
+            next: { revalidate: 86_400 },
+        });
+    } catch (error) {
+        throw new Error(`discord rpc unreachable: ${applicationId}`, { cause: error });
+    }
+    if (!response.ok) {
+        if (response.status === 404) {
+            return null;
+        }
+        if (response.status >= 500 || response.status === 429) {
+            throw new Error(`discord rpc upstream failed: ${applicationId} -> ${response.status}`, {
+                cause: new Error(`HTTP ${response.status}`),
+            });
+        }
+        warnDev(`discord app failed: ${response.status}`);
+        return null;
+    }
+    let json: DiscordRpcResponse;
+    try {
+        json = (await response.json()) as DiscordRpcResponse;
+    } catch (error) {
+        throw new Error(`discord rpc malformed response: ${applicationId}`, { cause: error });
+    }
+    const gameId = json.linked_games?.[0]?.id ?? json.id ?? applicationId;
+    return {
+        id: json.id ?? applicationId,
+        name: json.name ?? "",
+        icon: json.icon ?? null,
+        iconUrl: discordAppIconUrl(applicationId, json.icon ?? null),
+        coverImage: json.cover_image ?? null,
+        coverUrl: discordAppCoverUrl(applicationId, json.cover_image ?? null),
+        gameId,
+        gameUrl: discordGameUrl(gameId),
+    };
+}