perf: optimize branded 404 artwork

server.js

@@ -24,6 +24,9 @@ const REQUEST_MAX_BYTES = 6 * 1024 * 1024;
 const API_READ_LIMIT_PER_MINUTE = 120;
 const MEDIA_READ_LIMIT_PER_MINUTE = 600;
 const SSE_HEARTBEAT_MS = 25_000;
+const IMMUTABLE_CACHE_CONTROL = 'public, max-age=31536000, immutable';
+const REVALIDATING_CACHE_CONTROL = 'public, max-age=300, must-revalidate';
+const FINGERPRINTED_ASSET = /\.[a-f0-9]{8,}\.[a-z0-9]+$/i;
 const events = new Set();
 const DISCOVERY_ROUTES = new Set([
   '/openapi.json',
@@ -152,6 +155,8 @@ const server = http.createServer(async (req, res) => {
     }
 
     if (req.method === 'GET' && url.pathname.startsWith('/assets/')) {
+      const isVersioned = url.searchParams.has('v') || FINGERPRINTED_ASSET.test(url.pathname);
+      res.setHeader('Cache-Control', isVersioned ? IMMUTABLE_CACHE_CONTROL : REVALIDATING_CACHE_CONTROL);
       return sendFile(res, `./public${url.pathname}`);
     }