feat(server): lightweight s3 client (#14348)

#### PR Dependency Tree


* **PR #14348** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Added a dedicated S3-compatible client package and expanded
S3-compatible storage config (endpoint, region, forcePathStyle,
requestTimeoutMs, minPartSize, presign options, sessionToken).
* Document sync now broadcasts batched/compressed doc updates for more
efficient real-time syncing.

* **Tests**
* New unit and benchmark tests for base64 utilities and S3 multipart
listing; updated storage-related tests to match new formats.

<sub>✏️ Tip: You can customize this high-level summary in your review
settings.</sub>
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/common/nbstore/src/impls/cloud/socket.ts

@@ -30,6 +30,15 @@ interface ServerEvents {
     timestamp: number;
     editor: string;
   };
+  'space:broadcast-doc-updates': {
+    spaceType: string;
+    spaceId: string;
+    docId: string;
+    updates: string[];
+    timestamp: number;
+    editor?: string;
+    compressed?: boolean;
+  };
 
   'space:collect-awareness': {
     spaceType: string;
@@ -124,33 +133,42 @@ export type ClientEventsMap = {
 
 export type Socket = SocketIO<ServerEventsMap, ClientEventsMap>;
 
-export function uint8ArrayToBase64(array: Uint8Array): Promise<string> {
-  return new Promise<string>(resolve => {
-    // Create a blob from the Uint8Array
-    const blob = new Blob([array]);
+type BufferConstructorLike = {
+  from(
+    data: Uint8Array | string,
+    encoding?: string
+  ): Uint8Array & {
+    toString(encoding: string): string;
+  };
+};
 
-    const reader = new FileReader();
-    reader.onload = function () {
-      const dataUrl = reader.result as string | null;
-      if (!dataUrl) {
-        resolve('');
-        return;
-      }
-      // The result includes the `data:` URL prefix and the MIME type. We only want the Base64 data
-      const base64 = dataUrl.split(',')[1];
-      resolve(base64);
-    };
+const BufferCtor = (globalThis as { Buffer?: BufferConstructorLike }).Buffer;
+const CHUNK_SIZE = 0x8000;
 
-    reader.readAsDataURL(blob);
-  });
+export async function uint8ArrayToBase64(array: Uint8Array): Promise<string> {
+  if (BufferCtor) {
+    return BufferCtor.from(array).toString('base64');
+  }
+
+  let binary = '';
+  for (let i = 0; i < array.length; i += CHUNK_SIZE) {
+    const chunk = array.subarray(i, i + CHUNK_SIZE);
+    binary += String.fromCharCode(...chunk);
+  }
+  return btoa(binary);
 }
 
 export function base64ToUint8Array(base64: string) {
+  if (BufferCtor) {
+    return new Uint8Array(BufferCtor.from(base64, 'base64'));
+  }
+
   const binaryString = atob(base64);
-  const binaryArray = [...binaryString].map(function (char) {
-    return char.charCodeAt(0);
-  });
-  return new Uint8Array(binaryArray);
+  const bytes = new Uint8Array(binaryString.length);
+  for (let i = 0; i < binaryString.length; i++) {
+    bytes[i] = binaryString.charCodeAt(i);
+  }
+  return bytes;
 }
 
 let authMethod: