Speed up timeline load with portrait thumbs, bootstrap API, and caching.

Add catalog bootstrap endpoint, portrait thumbnail pipeline, lazy queued timeline images, gzip compression, and 3D texture throttling with code-split VirtualGallery.

client/src/hooks/useQueuedImageSrc.ts

@@ -0,0 +1,54 @@
+import { useEffect, useState } from 'react';
+
+const MAX_CONCURRENT = 6;
+const queue: Array<() => void> = [];
+let inFlight = 0;
+
+function pumpQueue() {
+  while (inFlight < MAX_CONCURRENT && queue.length > 0) {
+    const next = queue.shift();
+    if (next) next();
+  }
+}
+
+function enqueueLoad(run: () => void) {
+  return new Promise<void>((resolve) => {
+    const task = () => {
+      inFlight++;
+      run();
+      resolve();
+      inFlight--;
+      pumpQueue();
+    };
+    queue.push(task);
+    pumpQueue();
+  });
+}
+
+/**
+ * Limits parallel image URL activation so hundreds of timeline portraits
+ * do not saturate the browser connection pool at once.
+ */
+export function useQueuedImageSrc(src: string | null | undefined): string | undefined {
+  const [activeSrc, setActiveSrc] = useState<string | undefined>(undefined);
+
+  useEffect(() => {
+    if (!src) {
+      setActiveSrc(undefined);
+      return;
+    }
+
+    let cancelled = false;
+    setActiveSrc(undefined);
+
+    enqueueLoad(() => {
+      if (!cancelled) setActiveSrc(src);
+    });
+
+    return () => {
+      cancelled = true;
+    };
+  }, [src]);
+
+  return activeSrc;
+}