Add error logging to bare rescue in send_req.cr

[hahwul]

Description

src/deliver/send_req.cr has a bare rescue block (line 44) that silently swallows all exceptions during HTTP request delivery.

rescue
ensure
  wg.done
end

The error should be logged at debug level before being swallowed, similar to how send_elasticsearch.cr handles it in its inner rescue.

Suggested fix

rescue e
  @logger.debug "Exception during request delivery"
  @logger.debug_sub e
ensure
  wg.done
end