fix(storage-s3): encode filename in generated URL (#14438)

### What

This PR updates the `getGenerateURL` function in the `s3-storage`
adapter to properly encode filenames using `encodeURIComponent` when
constructing file URLs. This ensures that the URL is properly encoded
when using the `disablePayloadAccessControl` option.

 ### Why

Without URL encoding, filenames containing special characters (spaces,
unicode characters, special symbols, etc.) can break URL generation and
lead to:
- 404 errors when accessing files with special characters 
- Malformed URLs that don't properly resolve 
- Security issues with improperly escaped characters

###  How

The fix wraps the filename parameter with `encodeURIComponent()` in the
URL construction, similar to how it is done in the [storage-vercel-blob
package](https://github.com/payloadcms/payload/blob/53d85574d8405f45423871ccf1da3209371ad2da/packages/storage-vercel-blob/src/generateURL.ts#L12).

###  Example:
- Before: `https://s3.endpoint.com/bucket/my file.jpg` (breaks)
- After: `https://s3.endpoint.com/bucket/my%20file.jpg` (works
correctly)

Author: jhb-dev

packages/storage-s3/src/generateURL.ts

@@ -12,5 +12,5 @@ export const getGenerateURL =
   ({ bucket, config: { endpoint } }: Args): GenerateURL =>
   ({ filename, prefix = '' }) => {
     const stringifiedEndpoint = typeof endpoint === 'string' ? endpoint : endpoint?.toString()
-    return `${stringifiedEndpoint}/${bucket}/${path.posix.join(prefix, filename)}`
+    return `${stringifiedEndpoint}/${bucket}/${path.posix.join(prefix, encodeURIComponent(filename))}`
   }