refactor: simplify .env.example and add bulk sync capabilities

- Simplify .env.example to show actual config values instead of instructions
- Add blockchain core, coordinator API, and marketplace web example sections
- Add bulk import functionality to ChainSync for faster catchup
- Add fetch_blocks_range and bulk_import_from methods with batching
- Add init-production command to genesis CLI for production chain setup
- Add HTTP client management with configurable batch size and poll interval

apps/blockchain-node/src/aitbc_chain/sync_cli.py

@@ -0,0 +1,42 @@
+#!/usr/bin/env python3
+"""
+Standalone bulk sync utility for fast catch-up.
+Usage: python -m aitbc_chain.sync_cli --source http://10.1.223.40:8006 [--batch-size 100]
+"""
+
+import argparse
+import asyncio
+import sys
+from pathlib import Path
+
+# Add src to path for standalone execution
+sys.path.insert(0, str(Path(__file__).parent))
+
+from aitbc_chain.config import Settings, settings
+from aitbc_chain.database import session_scope
+from aitbc_chain.sync import ChainSync
+
+
+async def main() -> None:
+    parser = argparse.ArgumentParser(description="Bulk import blocks from a leader to catch up quickly")
+    parser.add_argument("--source", default="http://10.1.223.40:8006", help="Source RPC URL")
+    parser.add_argument("--import-url", default="http://127.0.0.1:8006", help="Local RPC URL for import")
+    parser.add_argument("--batch-size", type=int, default=100, help="Blocks per batch")
+    parser.add_argument("--poll-interval", type=float, default=0.2, help="Seconds between batches")
+    args = parser.parse_args()
+
+    sync = ChainSync(
+        session_factory=session_scope,
+        chain_id=settings.chain_id,
+        batch_size=args.batch_size,
+        poll_interval=args.poll_interval,
+    )
+    try:
+        imported = await sync.bulk_import_from(args.source, import_url=args.import_url)
+        print(f"[+] Bulk sync complete: imported {imported} blocks")
+    finally:
+        await sync.close()
+
+
+if __name__ == "__main__":
+    asyncio.run(main())