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/dev/aitbc-pythonpath.pth

@@ -0,0 +1,17 @@
+# Add project paths to Python path for imports
+import sys
+from pathlib import Path
+
+# Get the directory where this .pth file is located
+project_root = Path(__file__).parent
+
+# Add package source directories
+sys.path.insert(0, str(project_root / "packages" / "py" / "aitbc-core" / "src"))
+sys.path.insert(0, str(project_root / "packages" / "py" / "aitbc-crypto" / "src"))
+sys.path.insert(0, str(project_root / "packages" / "py" / "aitbc-p2p" / "src"))
+sys.path.insert(0, str(project_root / "packages" / "py" / "aitbc-sdk" / "src"))
+
+# Add app source directories
+sys.path.insert(0, str(project_root / "apps" / "coordinator-api" / "src"))
+sys.path.insert(0, str(project_root / "apps" / "wallet-daemon" / "src"))
+sys.path.insert(0, str(project_root / "apps" / "blockchain-node" / "src"))