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/examples/quick_job.py

@@ -0,0 +1,42 @@
+#!/usr/bin/env python3
+"""
+Quick job submission and payment
+Usage: python3 quick_job.py "your prompt"
+"""
+
+import subprocess
+import sys
+import time
+
+if len(sys.argv) < 2:
+    print("Usage: python3 quick_job.py \"your prompt\"")
+    sys.exit(1)
+
+prompt = sys.argv[1]
+
+print(f"🚀 Submitting job: '{prompt}'")
+
+# Submit job
+result = subprocess.run(
+    f'cd ../cli && python3 client.py submit inference --prompt "{prompt}"',
+    shell=True,
+    capture_output=True,
+    text=True
+)
+
+# Extract job ID
+job_id = None
+for line in result.stdout.split('\n'):
+    if "Job ID:" in line:
+        job_id = line.split()[-1]
+        break
+
+if job_id:
+    print(f"✅ Job submitted: {job_id}")
+    print("\n💡 Next steps:")
+    print(f"   1. Start miner: python3 cli/miner.py mine")
+    print(f"   2. Check status: python3 cli/client.py status {job_id}")
+    print(f"   3. After completion, pay with:")
+    print(f"      cd home/client && python3 wallet.py send 25.0 $(cd home/miner && python3 wallet.py address | grep Address | cut -d' ' -f4) 'Payment for {job_id}'")
+else:
+    print("❌ Failed to submit job")