fix(km): normalize legacy timestamps

apps/api/tests/test_knowledge_repository_read_model.py

@@ -86,10 +86,21 @@ def test_knowledge_read_model_normalizes_legacy_tag_shapes_and_null_counts() ->
 
     json_tag_entry = repo._to_model(_record(tags='["telegram", " ai_loop "]', view_count=None))
     scalar_tag_entry = repo._to_model(_record(tags="telegram"))
+    bad_count_entry = repo._to_model(_record(view_count="not-a-number"))
 
     assert json_tag_entry.tags == ["telegram", "ai_loop"]
     assert json_tag_entry.view_count == 0
     assert scalar_tag_entry.tags == ["telegram"]
+    assert bad_count_entry.view_count == 0
+
+
+def test_knowledge_read_model_fills_missing_legacy_timestamps() -> None:
+    repo = KnowledgeDBRepository(db=object())  # type: ignore[arg-type]
+
+    entry = repo._to_model(_record(created_at=None, updated_at=None))
+
+    assert entry.created_at is not None
+    assert entry.updated_at is not None
 
 
 def test_knowledge_read_model_defaults_null_or_blank_category() -> None: