AshAdmin ships a hardcoded CSP nonce, allowing nonce-based CSP bypass

Use of Insufficiently Random Values vulnerability in ash-project ash_admin ships a hardcoded, publicly known CSP nonce, defeating nonce-based Content-Security-Policy protection. When mounted without :csp_nonce_assign_key, AshAdmin.Router.ash_admin/2 defaulted the img, style, and script nonces to the literal constant ash_admin-Ed55GFnX, which AshAdmin.Layouts wrote verbatim into the nonce attribute of its inline <style> and <script> tags on every response. The value is a compile-time constant published in the repository and is never rotated per request. If an application's CSP script-src allow-lists that documented default, any HTML-injection sink on an admin page can reuse the known nonce to run inline scripts the policy was meant to block. The fix generates a fresh random nonce per request. This issue affects ash_admin: from 0.10.8 before 1.3.1.