Add several boards per level, CM1/CM2 levels and the CE1 'plage des sons' pilot board (0.6.0)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

data/curriculum/ce1_accords_groupe_nominal.json

@@ -3,6 +3,13 @@
   "region_id": "foret_des_accords",
   "chapter_id": "accords_groupe_nominal",
   "title": "Les accords dans le groupe nominal",
-  "rule_ids": ["regle_accord_adjectif", "regle_pluriel_nom", "regle_accord_determinant"],
+  "region_title": "La forêt des accords",
+  "order": 1,
+  "backdrop": "forest",
+  "rule_ids": [
+    "regle_accord_adjectif",
+    "regle_pluriel_nom",
+    "regle_accord_determinant"
+  ],
   "review_status": "draft"
 }

data/curriculum/ce1_sons_et_lettres.json

@@ -0,0 +1,15 @@
+{
+  "level": "CE1",
+  "region_id": "plage_des_sons",
+  "chapter_id": "sons_et_lettres",
+  "title": "Les sons et les lettres",
+  "region_title": "La plage des sons",
+  "order": 2,
+  "backdrop": "beach",
+  "rule_ids": [
+    "regle_s_ss",
+    "regle_c_cedille",
+    "regle_m_devant_mbp"
+  ],
+  "review_status": "draft"
+}

data/curriculum/ce2_homophones_grammaticaux.json

@@ -3,6 +3,9 @@
   "region_id": "marais_des_homophones",
   "chapter_id": "homophones_grammaticaux",
   "title": "Les homophones grammaticaux",
+  "region_title": "Le marais des homophones",
+  "order": 1,
+  "backdrop": "marsh",
   "rule_ids": [
     "regle_homophone_a_a",
     "regle_homophone_et_est",