Add sys import to test files and remove obsolete integration tests

- Add sys import to 29 test files across agent-coordinator, blockchain-event-bridge, blockchain-node, and coordinator-api
- Remove apps/blockchain-event-bridge/tests/test_integration.py (obsolete bridge integration tests)
- Remove apps/coordinator-api/tests/test_integration.py (obsolete API integration tests)
- Implement GPU registration in marketplace_gpu.py with GPURegistry model persistence

apps/trading-engine/tests/test_unit_trading_engine.py

@@ -0,0 +1,89 @@
+"""Unit tests for trading engine service"""
+
+import pytest
+import sys
+import sys
+from pathlib import Path
+from datetime import datetime
+
+
+from main import app, Order, Trade, OrderBookEntry
+
+
+@pytest.mark.unit
+def test_app_initialization():
+    """Test that the FastAPI app initializes correctly"""
+    assert app is not None
+    assert app.title == "AITBC Trading Engine"
+    assert app.version == "1.0.0"
+
+
+@pytest.mark.unit
+def test_order_model():
+    """Test Order model"""
+    order = Order(
+        order_id="order_123",
+        symbol="AITBC/BTC",
+        side="buy",
+        type="limit",
+        quantity=100.0,
+        price=0.00001,
+        user_id="user_123",
+        timestamp=datetime.utcnow()
+    )
+    assert order.order_id == "order_123"
+    assert order.symbol == "AITBC/BTC"
+    assert order.side == "buy"
+    assert order.type == "limit"
+    assert order.quantity == 100.0
+    assert order.price == 0.00001
+    assert order.user_id == "user_123"
+
+
+@pytest.mark.unit
+def test_order_model_market_order():
+    """Test Order model for market order"""
+    order = Order(
+        order_id="order_123",
+        symbol="AITBC/BTC",
+        side="sell",
+        type="market",
+        quantity=50.0,
+        user_id="user_123",
+        timestamp=datetime.utcnow()
+    )
+    assert order.type == "market"
+    assert order.price is None
+
+
+@pytest.mark.unit
+def test_trade_model():
+    """Test Trade model"""
+    trade = Trade(
+        trade_id="trade_123",
+        symbol="AITBC/BTC",
+        buy_order_id="buy_order_123",
+        sell_order_id="sell_order_123",
+        quantity=100.0,
+        price=0.00001,
+        timestamp=datetime.utcnow()
+    )
+    assert trade.trade_id == "trade_123"
+    assert trade.symbol == "AITBC/BTC"
+    assert trade.buy_order_id == "buy_order_123"
+    assert trade.sell_order_id == "sell_order_123"
+    assert trade.quantity == 100.0
+    assert trade.price == 0.00001
+
+
+@pytest.mark.unit
+def test_order_book_entry_model():
+    """Test OrderBookEntry model"""
+    entry = OrderBookEntry(
+        price=0.00001,
+        quantity=1000.0,
+        orders_count=5
+    )
+    assert entry.price == 0.00001
+    assert entry.quantity == 1000.0
+    assert entry.orders_count == 5