feat: address PR review comments — unassign/sync bank questions, blank quiz creation, deactivate redirect, remove duplicate tab titles

- Use Symfony ObjectMapper for BankQuestion/BankAnswer → Question/Answer copy (#[Map(if: false)] on id, season, etc.)
- Track created Question on BankQuestionUsage (nullable FK, onDelete: SET NULL) for unassign/sync support
- Add unassign route: removes the Question copy + usage record
- Add sync route: pushes bank question edits to a finalized-not-started quiz copy
- Auto-sync non-finalized quiz copies on bank question edit; flash warning for finalized-not-started
- Add blank quiz creation (no XLSX required) with new route + template
- Deactivate quiz button now stays on the quiz overview page (redirect_quiz hidden field)
- Remove duplicate h4 titles below the tab bar on all season tabs
- Add migration for bank_question_usage.question_id
- Add Dutch translations for all new strings

templates/backoffice/season/tab_question_bank.html.twig

@@ -1,6 +1,5 @@
-<div class="d-flex align-items-center mb-3">
-    <h4 class="mb-0 pe-2">{{ 'Question bank'|trans }}</h4>
-    <a class="link" href="{{ path('tvdt_backoffice_question_bank_new', {seasonCode: season.seasonCode}) }}">{{ 'Add'|trans }}</a>
+<div class="mb-3">
+    <a class="btn btn-sm btn-outline-primary" href="{{ path('tvdt_backoffice_question_bank_new', {seasonCode: season.seasonCode}) }}">{{ 'Add question'|trans }}</a>
 </div>
 
     <div class="d-flex align-items-center flex-wrap gap-2 mb-3">
@@ -51,7 +50,23 @@
                     {% endif %}
                 </td>
                 <td>
-                    {{ bankQuestion.usages|map(usage => usage.quiz.name)|join(', ') }}
+                    {% for usage in bankQuestion.usages %}
+                        <div class="d-flex align-items-center gap-1">
+                            <span>{{ usage.quiz.name }}</span>
+                            <form action="{{ path('tvdt_backoffice_question_bank_unassign', {seasonCode: season.seasonCode, bankQuestion: bankQuestion.id, usage: usage.id}) }}"
+                                  method="POST" class="d-inline">
+                                <input type="hidden" name="_token" value="{{ csrf_token('unassign_bank_question') }}">
+                                <button type="submit" class="btn btn-sm btn-link p-0 text-danger" title="{{ 'Unassign'|trans }}">&times;</button>
+                            </form>
+                            {% if usage.quiz.isFinalized %}
+                                <form action="{{ path('tvdt_backoffice_question_bank_sync', {seasonCode: season.seasonCode, bankQuestion: bankQuestion.id, usage: usage.id}) }}"
+                                      method="POST" class="d-inline">
+                                    <input type="hidden" name="_token" value="{{ csrf_token('sync_bank_question') }}">
+                                    <button type="submit" class="btn btn-sm btn-link p-0 text-primary" title="{{ 'Sync latest changes to this quiz'|trans }}">&#8635;</button>
+                                </form>
+                            {% endif %}
+                        </div>
+                    {% endfor %}
                 </td>
                 <td class="text-end">
                     <div class="d-inline-flex align-items-center gap-2">