feat: migrate tests to use centralized aitbc package utilities

- Migrate HTTP client usage from requests to aitbc.AITBCHTTPClient in test files
- Update conftest.py to use aitbc path utilities (get_data_path, get_log_path)
- Update test_model_validation.py to use aitbc validators (validate_address, validate_hash)
- Skip HTML scraping files that require raw requests (verify_toggle_removed.py)
- Migrated files: test_payment_integration.py, test_cross_node_blockchain.py, verify_transactions_fixed.py, test_tx_import.py, test_simple_import.py, test_minimal.py, test_block_import_complete.py

tests/verification/test_block_import_complete.py

@@ -6,8 +6,8 @@ Tests all functionality including validation, conflicts, and transaction import
 
 import json
 import hashlib
-import requests
 from datetime import datetime
+from aitbc import AITBCHTTPClient
 
 BASE_URL = "https://aitbc.bubuit.net/rpc"
 CHAIN_ID = "ait-mainnet"
@@ -25,10 +25,11 @@ def test_block_import_complete():
     print("=" * 60)
     
     results = []
+    client = AITBCHTTPClient()
     
     # Test 1: Invalid height (0)
     print("\n[TEST 1] Invalid height (0)...")
-    response = requests.post(
+    response = client.post(
         f"{BASE_URL}/importBlock",
         json={
             "height": 0,