CSP adherence: fix magic links console logging (#1989)

* CSP: fix magic link console logging by including nonce in the script tag

* Remove unused back-nav controller

Unused since c0f842427d

Eliminates a potential CSP violation with javascript: URI

app/javascript/controllers/back_navigation_controller.js

@@ -1,13 +0,0 @@
-import { Controller } from "@hotwired/stimulus"
-
-export default class extends Controller {
-  static values = { fallbackDestination: String }
-
-  connect() {
-    if (history.state.turbo?.restorationIndex > 0) {
-      this.element.href = "javascript:history.back()"
-    } else {
-      this.element.href = this.fallbackDestinationValue
-    }
-  }
-}