rename: chapitre/projet templates to chapter/project

Standardize French template names to English across blueprints,
content files, PHP templates, Vue components and Pinia stores.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

public/site/blueprints/pages/projet.yml

@@ -1,28 +0,0 @@
-title: Projet
-
-columns:
-  main:
-    width: 2/3
-    sections:
-      fields:
-        type: fields
-        fields:
-          subtitle:
-            label: Sous-titre
-            type: text
-            width: 1/2
-          cover:
-            label: Image de couverture
-            type: files
-            multiple: false
-            width: 1/2
-      pages:
-        label: Récits
-        type: pages
-        template: narrative
-  sidebar:
-    width: 1/3
-    sections:
-      files:
-        label: Fichiers
-        type: files