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/blockchain-explorer/tests/test_unit_blockchain_explorer.py

@@ -0,0 +1,120 @@
+"""Unit tests for blockchain explorer service"""
+
+import pytest
+import sys
+import sys
+from pathlib import Path
+
+
+from main import app, TransactionSearch, BlockSearch, AnalyticsRequest
+
+
+@pytest.mark.unit
+def test_app_initialization():
+    """Test that the FastAPI app initializes correctly"""
+    assert app is not None
+    assert app.title == "AITBC Blockchain Explorer"
+    assert app.version == "0.1.0"
+
+
+@pytest.mark.unit
+def test_transaction_search_model():
+    """Test TransactionSearch model"""
+    search = TransactionSearch(
+        address="0x1234567890abcdef",
+        amount_min=1.0,
+        amount_max=100.0,
+        tx_type="transfer",
+        since="2024-01-01",
+        until="2024-12-31",
+        limit=50,
+        offset=0
+    )
+    assert search.address == "0x1234567890abcdef"
+    assert search.amount_min == 1.0
+    assert search.amount_max == 100.0
+    assert search.tx_type == "transfer"
+    assert search.limit == 50
+
+
+@pytest.mark.unit
+def test_transaction_search_defaults():
+    """Test TransactionSearch with default values"""
+    search = TransactionSearch()
+    assert search.address is None
+    assert search.amount_min is None
+    assert search.amount_max is None
+    assert search.tx_type is None
+    assert search.limit == 50
+    assert search.offset == 0
+
+
+@pytest.mark.unit
+def test_block_search_model():
+    """Test BlockSearch model"""
+    search = BlockSearch(
+        validator="0x1234567890abcdef",
+        since="2024-01-01",
+        until="2024-12-31",
+        min_tx=5,
+        limit=50,
+        offset=0
+    )
+    assert search.validator == "0x1234567890abcdef"
+    assert search.min_tx == 5
+    assert search.limit == 50
+
+
+@pytest.mark.unit
+def test_block_search_defaults():
+    """Test BlockSearch with default values"""
+    search = BlockSearch()
+    assert search.validator is None
+    assert search.since is None
+    assert search.until is None
+    assert search.min_tx is None
+    assert search.limit == 50
+    assert search.offset == 0
+
+
+@pytest.mark.unit
+def test_analytics_request_model():
+    """Test AnalyticsRequest model"""
+    request = AnalyticsRequest(
+        period="24h",
+        granularity="hourly",
+        metrics=["total_transactions", "volume"]
+    )
+    assert request.period == "24h"
+    assert request.granularity == "hourly"
+    assert request.metrics == ["total_transactions", "volume"]
+
+
+@pytest.mark.unit
+def test_analytics_request_defaults():
+    """Test AnalyticsRequest with default values"""
+    request = AnalyticsRequest()
+    assert request.period == "24h"
+    assert request.granularity is None
+    assert request.metrics == []
+
+
+@pytest.mark.unit
+def test_transaction_search_limit_validation():
+    """Test TransactionSearch limit validation"""
+    search = TransactionSearch(limit=1000)
+    assert search.limit == 1000
+
+
+@pytest.mark.unit
+def test_transaction_search_offset_validation():
+    """Test TransactionSearch offset validation"""
+    search = TransactionSearch(offset=100)
+    assert search.offset == 100
+
+
+@pytest.mark.unit
+def test_block_search_limit_validation():
+    """Test BlockSearch limit validation"""
+    search = BlockSearch(limit=500)
+    assert search.limit == 500