fix: move imports to local __init__.py files to make less noise on the routers

app/problems/grade_1/__init__.py

@@ -0,0 +1,15 @@
+from app.problems.grade_1.compose_and_decompose_numbers import (
+    compose_and_decompose_numbers,
+)
+from app.problems.grade_1.join_pictures_with_quantity import (
+    join_pictures_with_quantity,
+)
+from app.problems.grade_1.sum_with_image_reference import sum_with_image_reference
+from app.problems.grade_1.where_are_more_items import where_are_more_items
+
+__all__ = [
+    "compose_and_decompose_numbers",
+    "join_pictures_with_quantity",
+    "sum_with_image_reference",
+    "where_are_more_items",
+]