feat: add board goal schemas and validation

backend/tests/test_board_schema.py

@@ -0,0 +1,20 @@
+import pytest
+
+from app.schemas.boards import BoardCreate
+
+
+def test_goal_board_requires_objective_and_metrics():
+    with pytest.raises(ValueError):
+        BoardCreate(name="Goal Board", slug="goal", board_type="goal")
+
+    BoardCreate(
+        name="Goal Board",
+        slug="goal",
+        board_type="goal",
+        objective="Launch onboarding",
+        success_metrics={"emails": 3},
+    )
+
+
+def test_general_board_allows_missing_objective():
+    BoardCreate(name="General", slug="general", board_type="general")