Update blueprints for multilingual support

- Extract investigations field to separate file for reusability
- Fix investigations query to work with multilingual pages
- Use site.find() instead of page() for multilingual compatibility

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

site/blueprints/fields/investigations.yml

@@ -0,0 +1,9 @@
+label: Enquêtes
+type: pages
+parent: page('enquetes')
+layout: cards
+text: "{{ page.title }}, {{ page.subtitle }}"
+info: "{{ page.incidentConsequences }} à {{ page.incidentLocation }}"
+image:
+  cover: true
+  ratio: 16/9