Add chunked uploads and raise storage rate to GHS 0.30/GB/month.

Large files upload in 5 MB chunks (hosting file manager pattern) for the
transfer UI and Ladill Mail S2S API, with no app-level file size cap when
TRANSFER_MAX_FILE_BYTES=0.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/Services/Transfer/TransferService.php

@@ -38,7 +38,7 @@ class TransferService
             throw new RuntimeException("You can upload up to {$maxFiles} files per transfer.");
         }
 
-        $maxBytes = (int) config('transfer.max_file_bytes', 524288000);
+        $maxBytes = (int) config('transfer.max_file_bytes', 0);
         $retentionDays = (int) ($data['retention_days'] ?? config('transfer.default_retention_days', 30));
         $retentionDays = max(1, min(365, $retentionDays));
 
@@ -64,7 +64,7 @@ class TransferService
                     continue;
                 }
 
-                if ($file->getSize() > $maxBytes) {
+                if ($maxBytes > 0 && $file->getSize() > $maxBytes) {
                     throw new RuntimeException($file->getClientOriginalName().' exceeds the maximum file size.');
                 }