Update sandbox retention policy details (#933)

Clarified sandbox data retention policy and error handling.

<!-- CURSOR_SUMMARY -->
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> [!NOTE]
> Clarifies that sandbox data retention is 30 days from creation (not
extended by resumes) and specifies NotFound errors when resuming
deleted/nonexistent sandboxes.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
8f9706f. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

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Co-authored-by: Vasek Mlejnsky <vasek@e2b.dev>

Author: mishushakov

apps/web/src/app/(docs)/docs/sandbox/persistence/page.mdx

@@ -259,4 +259,5 @@ If you resume the sandbox, the service will be accessible again but you need to
 - Pausing a sandbox takes about 4 seconds per 1 GiB of RAM
 - Resuming a sandbox takes about 1 second
 - Sandbox can be used up to 30 days
-  - After 30 days from the initial sandbox create call, the data may be deleted and you will not be able to resume it. Attempting to resume a sandbox that was deleted or does not exist will result in the `NotFoundError` in the JavaScript SDK or the `NotFoundException` in the Python SDK
+  - After 30 days from the sandbox creation, the sandbox data may be deleted. This retention period is based on the original sandbox creation date and is not extended or reset by subsequent resumes. Attempting to resume a sandbox that was deleted or does not exist will result in a `NotFoundError` (JavaScript SDK) or `NotFoundException` (Python SDK).
+