feat(storage/s3): make S3 socket timeout configurable

The hardcoded socketTimeout: 3000 (introduced in d682bc0 along with
stream-based downloads) aborts in-flight R2/S3 GetObject body sockets
whenever the response stream is paused for >3s by backpressure from
either the client response or the merge upload, surfacing as
ECONNRESET on /download/<id>.

Expose STORAGE_S3_SOCKET_TIMEOUT_MS so deployments hitting this can
raise it without forking. Default raised to 10000 to give backpressure
pauses more headroom on first-download proxy paths.

Author: devunt

lib/schemas.ts

@@ -8,6 +8,7 @@ export const envStorageDriverSchema = type.or(
     'AWS_ENDPOINT_URL?': 'string.url',
     'AWS_ACCESS_KEY_ID?': 'string',
     'AWS_SECRET_ACCESS_KEY?': 'string',
+    'STORAGE_S3_SOCKET_TIMEOUT_MS': 'number = 10000',
   },
   {
     STORAGE_DRIVER: type.unit('filesystem'),

lib/storage.ts

@@ -527,7 +527,7 @@ class S3Adapter implements StorageAdapter {
       region: env.AWS_REGION,
       requestHandler: new NodeHttpHandler({
         httpsAgent: agent,
-        socketTimeout: 3000,
+        socketTimeout: env.STORAGE_S3_SOCKET_TIMEOUT_MS,
       }),
     })