feat(memory): add memory consolidation task and switch source_episode_ids to JSON

- Added `memory_consolidation` to the task list and updated `__all__` in test files.
- Updated `source_episode_ids` in `Fact` model to use JSON for cross-database compatibility.
- Revised related database migrations to use JSONB instead of ARRAY.
- Adjusted test concurrency in Makefile for improved test performance.

backend/tests/tasks/test_celery_config.py

@@ -304,10 +304,18 @@ class TestTaskModuleExports:
         assert hasattr(tasks, "sync")
         assert hasattr(tasks, "workflow")
         assert hasattr(tasks, "cost")
+        assert hasattr(tasks, "memory_consolidation")
 
     def test_tasks_all_attribute_is_correct(self):
         """Test that __all__ contains all expected module names."""
         from app import tasks
 
-        expected_modules = ["agent", "git", "sync", "workflow", "cost"]
+        expected_modules = [
+            "agent",
+            "git",
+            "sync",
+            "workflow",
+            "cost",
+            "memory_consolidation",
+        ]
         assert set(tasks.__all__) == set(expected_modules)