feat: move data directory from repository to system location

✅ Data Directory Restructure
- Moved /opt/aitbc/data to /var/lib/aitbc/data (proper system location)
- Updated all production services to use system data path
- Updated systemd services to use system data path
- Created symlink for backward compatibility
- Created proper data directories in /var/lib/aitbc/data/

✅ Services Updated
- Marketplace: /var/lib/aitbc/data/marketplace
- Blockchain: /var/lib/aitbc/data/blockchain
- OpenClaw: /var/lib/aitbc/data/openclaw
- All services now using system data paths

✅ System Compliance
- Data stored in /var/lib/aitbc (FHS compliant)
- Repository no longer contains runtime data
- Backward compatibility maintained with symlink
- Production services using correct system paths

🚀 AITBC now follows proper system data directory structure!

production/services/blockchain_simple.py

@@ -81,7 +81,7 @@ class ProductionBlockchain:
     
     def __init__(self, node_id: str):
         self.node_id = node_id
-        self.data_dir = Path(f'/opt/aitbc/production/data/blockchain/{node_id}')
+        self.data_dir = Path(f'/var/lib/aitbc/data/blockchain/{node_id}')
         self.data_dir.mkdir(parents=True, exist_ok=True)
         
         # Initialize blockchain