refactor: organize scripts/, remove stale root dirs, clean up structure

scripts/ reorganization:
- Sort 14 loose root scripts into subfolders:
  blockchain/ (genesis, proposer, mock chain, testnet BTC)
  dev/ (CLI wrapper, dev services, OpenAPI gen, systemd setup, domain proxy)
  ops/ (coordinator proxy, remote tunnel)
  gpu/ (miner workflow)
- Merge scripts/testing/ into scripts/test/ (eliminate duplicate folder)
- Create scripts/examples/ for usage demos and simulations

Root-level cleanup:
- Move home/ (12 simulation scripts) → scripts/examples/
- Move dev-utils/ (2 files) → scripts/dev/
- Move protocols/receipts/sample → tests/fixtures/
- Delete stale src/ (duplicate of apps/blockchain-node/src/)
- Remove empty home/, dev-utils/, protocols/ directories

Documentation updates:
- Update docs/6_architecture/8_codebase-structure.md tree and table
- Update root README.md tree to reflect new structure

scripts/test/test_tx_import.py

@@ -0,0 +1,77 @@
+#!/usr/bin/env python3
+"""
+Test transaction import specifically
+"""
+
+import json
+import hashlib
+import requests
+
+BASE_URL = "https://aitbc.bubuit.net/rpc"
+CHAIN_ID = "ait-devnet"
+
+def compute_block_hash(height, parent_hash, timestamp):
+    """Compute block hash using the same algorithm as PoA proposer"""
+    payload = f"{CHAIN_ID}|{height}|{parent_hash}|{timestamp}".encode()
+    return "0x" + hashlib.sha256(payload).hexdigest()
+
+def test_transaction_import():
+    """Test importing a block with a single transaction"""
+    
+    print("Testing Transaction Import")
+    print("=" * 40)
+    
+    # Get current head
+    response = requests.get(f"{BASE_URL}/head")
+    head = response.json()
+    print(f"Current head: height={head['height']}")
+    
+    # Create a new block with one transaction
+    height = head["height"] + 1
+    parent_hash = head["hash"]
+    timestamp = "2026-01-29T10:20:00"
+    block_hash = compute_block_hash(height, parent_hash, timestamp)
+    
+    test_block = {
+        "height": height,
+        "hash": block_hash,
+        "parent_hash": parent_hash,
+        "proposer": "test-proposer",
+        "timestamp": timestamp,
+        "tx_count": 1,
+        "transactions": [{
+            "tx_hash": "0xtx123456789",
+            "sender": "0xsender123",
+            "recipient": "0xreceiver456",
+            "payload": {"to": "0xreceiver456", "amount": 1000000}
+        }]
+    }
+    
+    print(f"\nTest block data:")
+    print(json.dumps(test_block, indent=2))
+    
+    # Import the block
+    response = requests.post(
+        f"{BASE_URL}/blocks/import",
+        json=test_block
+    )
+    
+    print(f"\nImport response:")
+    print(f"  Status: {response.status_code}")
+    print(f"  Body: {response.json()}")
+    
+    # Check logs
+    print("\nChecking recent logs...")
+    import subprocess
+    result = subprocess.run(
+        ["ssh", "aitbc-cascade", "journalctl -u blockchain-node --since '30 seconds ago' | grep 'Importing transaction' | tail -1"],
+        capture_output=True,
+        text=True
+    )
+    if result.stdout:
+        print(f"Log: {result.stdout.strip()}")
+    else:
+        print("No transaction import logs found")
+
+if __name__ == "__main__":
+    test_transaction_import()