Feature/consent banner (#21)

* feat: add consent banner requirement for signers (B6)

- Add REQUIRE_CONSENT_KEY to AccountConfig for per-account toggle
- Add consent_given event type to SubmissionEvent for audit trail
- Add consent checkbox UI on last step of signing form (form.vue)
- Add isLastStep computed property and onConsentChange method
- Create API endpoint (submitter_consents#create) to record consent
- Add requireConsent prop passing from server via data attribute
- Add settings toggle in Account preferences page
- Add i18n translations for all 14 languages (JS + Rails)
- Submit button disabled until consent checkbox is checked

* fix: add REQUIRE_CONSENT_KEY to AccountConfigsController ALLOWED_KEYS

* fix: keep consent checkbox visible after checking (don't remove from DOM)

* fix: bind checkbox checked state to consentAccepted for step navigation sync

* fix: guard submitStep() against consent bypass via child component @submit events

app/controllers/account_configs_controller.rb

@@ -27,6 +27,7 @@ class AccountConfigsController < ApplicationController
     AccountConfig::DOCUMENT_FILENAME_FORMAT_KEY,
     AccountConfig::ENABLE_MCP_KEY,
     AccountConfig::IP_ALLOWLIST_KEY,
+    AccountConfig::REQUIRE_CONSENT_KEY
     AccountConfig::AUTO_ARCHIVE_DAYS_KEY,
     AccountConfig::REQUIRE_CONSENT_KEY,
     AccountConfig::REQUIRE_ID_VERIFICATION_KEY

app/javascript/submission_form/form.vue

@@ -1685,6 +1685,12 @@ export default {
       return this.$refs.areas.scrollIntoArea(area)
     },
     async submitStep (e) {
+      if (this.requireConsent && this.isLastStep && !this.consentAccepted) {
+        return
+      }
+
+      this.isSubmitting = true
+
       const forceComplete = e?.submitter?.getAttribute('name') === 'completed'
 
       if (this.requireConsent && !this.consentAccepted && (this.isLastStep || forceComplete)) {