feat: show a hint for the candidates textarea and gate translations in CI

Add a help hint on the add-candidates form explaining one candidate per
line, and translate it plus a few strings from the earlier reset-progress
feature that had been missed. Also add a CI step that re-runs
translation:extract and fails the build if it produces uncommitted
changes, so untranslated/stale strings can't slip through review again.

.github/workflows/ci.yml

@@ -95,6 +95,15 @@ jobs:
         id: rector
         continue-on-error: true
         run: docker compose exec -T php vendor/bin/rector process --dry-run --no-progress-bar --output-format=github
+      - name: Translations
+        id: translations
+        continue-on-error: true
+        run: |
+          docker compose exec -T php bin/console translation:extract --force --format=xliff --sort=asc nl
+          if ! git diff --exit-code -- translations; then
+            echo "::error::Translations are out of date. Run 'just translations' and commit the changes."
+            exit 1
+          fi
       - name: Check HTTP reachability
         run: curl -v --fail-with-body http://localhost
       - name: Assert all checks passed
@@ -113,6 +122,7 @@ jobs:
           check "Twig Coding Style" "${{ steps.twig_cs.outcome }}"
           check "PHPStan"          "${{ steps.phpstan.outcome }}"
           check "Rector"           "${{ steps.rector.outcome }}"
+          check "Translations"     "${{ steps.translations.outcome }}"
           exit $failed
 
   tests:

CLAUDE.md

@@ -306,6 +306,7 @@ GitHub Actions workflow (`.github/workflows/ci.yml`):
     - Twig-CS-Fixer style check
     - PHPStan static analysis
     - Rector dry-run
+    - Translation extraction check (fails if `translation:extract` produces uncommitted changes)
 3. **Integration Tests**:
     - Docker image build and start services
     - Database creation and migration

src/Form/AddCandidatesFormType.php

@@ -19,7 +19,9 @@ class AddCandidatesFormType extends AbstractType
     {
         $builder
             ->add('candidates', TextareaType::class, [
-                'label' => $this->translator->trans('Candidates'), 'translation_domain' => false,
+                'label' => $this->translator->trans('Candidates'),
+                'help' => $this->translator->trans('One candidate per line'),
+                'translation_domain' => false,
             ])
         ;
     }

translations/messages+intl-icu.nl.xliff

@@ -117,6 +117,10 @@
         <source>Are you sure you want to delete this quiz?</source>
         <target>Weet je zeker dat je deze test wilt verwijderen?</target>
       </trans-unit>
+      <trans-unit id="6XTrab." resname="Are you sure you want to reset progress for this candidate? Their given answers for this quiz will be deleted.">
+        <source>Are you sure you want to reset progress for this candidate? Their given answers for this quiz will be deleted.</source>
+        <target>Weet je zeker dat je de voortgang van deze kandidaat wilt resetten? De ingevulde antwoorden voor deze test worden verwijderd.</target>
+      </trans-unit>
       <trans-unit id="4bcq6sL" resname="Assign">
         <source>Assign</source>
         <target>Toewijzen</target>
@@ -161,6 +165,10 @@
         <source>Candidate not found</source>
         <target>Kandidaat niet gevonden</target>
       </trans-unit>
+      <trans-unit id="fl.hjdA" resname="Candidate progress reset">
+        <source>Candidate progress reset</source>
+        <target>Voortgang kandidaat gereset</target>
+      </trans-unit>
       <trans-unit id="QH4e_Ho" resname="Candidate renamed">
         <source>Candidate renamed</source>
         <target>Kandidaat hernoemd</target>
@@ -541,6 +549,10 @@
         <source>Number of dropouts:</source>
         <target>Aantal afvallers:</target>
       </trans-unit>
+      <trans-unit id="vxaREnf" resname="One candidate per line">
+        <source>One candidate per line</source>
+        <target>Eén kandidaat per regel</target>
+      </trans-unit>
       <trans-unit id="_SqArFZ" resname="Open">
         <source>Open</source>
         <target>Openen</target>
@@ -761,6 +773,10 @@
         <source>Reset password</source>
         <target>Wachtwoord herstellen</target>
       </trans-unit>
+      <trans-unit id="SSMxy68" resname="Reset progress">
+        <source>Reset progress</source>
+        <target>Voortgang resetten</target>
+      </trans-unit>
       <trans-unit id="eyayNGN" resname="Reset your password">
         <source>Reset your password</source>
         <target>Wachtwoord herstellen</target>