Y25-007 - [BUG] Exception `scans#create (ActionController::InvalidAuthenticityToken) "Can't verify`

[harrietc52]

Describe the bug
There is a repeated exception for Labware (prod):

An ActionController::InvalidAuthenticityToken occurred in scans#create:

  Can't verify CSRF token authenticity.

Acceptance Criteria

• Identify the root cause
• Finding and applying a solution
• Document progress + summary in the issue comments

Additional context

• URL : https://labwhere.psd.sanger.ac.uk/scans
• HTTP Method: POST
• IP address : 172.20.241.168
• Parameters : {"authenticity_token"=>"5a1FxPsWNsnyTCZ7pYOHx6UhC5RBg7Sif6wOd4xI3jhmWVyeuxFMH5oU9qoFPl_2vuu-3aFWcLD7LHrKmcBwSA", "scan"=>{"user_code"=>"", "location_barcode"=>"lw-exhausted-sbt-34674", "start_position"=>"", "labware_barcodes"=>""}, "commit"=>"Go!", "controller"=>"scans", "action"=>"create"}
• Timestamp : 2024-12-16 10:25:56 +0000
• Server : labw-prod-jammy
  • Rails root : /var/www/labwhere/releases/20240926125930
• Process: 403997