feat: drop old schema tables (trading_sessions, positions, reasoning_logs)

- Created migration script to drop old tables
- Removed old table creation from database.py
- Added tests to verify old tables are removed and new tables exist
- Migration script can be run standalone with: PYTHONPATH=. python api/migrations/002_drop_old_schema.py

tests/unit/test_old_schema_removed.py

@@ -0,0 +1,42 @@
+"""Verify old schema tables are removed."""
+
+import pytest
+from api.database import Database
+
+
+def test_old_tables_do_not_exist():
+    """Verify trading_sessions, old positions, reasoning_logs don't exist."""
+
+    db = Database(":memory:")
+
+    # Query sqlite_master for old tables
+    cursor = db.connection.execute("""
+        SELECT name FROM sqlite_master
+        WHERE type='table' AND name IN (
+            'trading_sessions', 'reasoning_logs'
+        )
+    """)
+
+    tables = cursor.fetchall()
+
+    assert len(tables) == 0, f"Old tables should not exist, found: {tables}"
+
+
+def test_new_tables_exist():
+    """Verify new schema tables exist."""
+
+    db = Database(":memory:")
+
+    cursor = db.connection.execute("""
+        SELECT name FROM sqlite_master
+        WHERE type='table' AND name IN (
+            'trading_days', 'holdings', 'actions'
+        )
+        ORDER BY name
+    """)
+
+    tables = [row[0] for row in cursor.fetchall()]
+
+    assert 'trading_days' in tables
+    assert 'holdings' in tables
+    assert 'actions' in tables