API: endpoint /schema (#78)

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

src/api/routes.py

@@ -1,5 +1,8 @@
 from flask_smorest import Blueprint
 
+from src.api.auth import require_token
+from src.db import schema as duckdb_schema
+
 bp = Blueprint(
     "api_v1",
     "api_v1",
@@ -12,3 +15,11 @@ bp = Blueprint(
 def health():
     """Sonde de santé, sans authentification."""
     return {"status": "ok"}
+
+
+@bp.route("/schema")
+@require_token
+def schema():
+    """Liste des colonnes disponibles dans le dataset DECP."""
+    cols = [{"name": name, "type": str(dtype)} for name, dtype in duckdb_schema.items()]
+    return {"columns": cols}