Replace hardcoded IPs with environment variables

Fixed hardcoded IP addresses in production code by replacing them with
environment variables or config settings:

- apps/blockchain-node/src/aitbc_chain/sync_cli.py: Use AITBC_SYNC_SOURCE
  and AITBC_SYNC_IMPORT_URL env vars for RPC URLs
- apps/blockchain-node/src/aitbc_chain/app.py: Use AITBC_TRUSTED_IPS
  env var for rate limiting bypass
- apps/coordinator-api/src/app/routers/client.py: Use settings.blockchain_rpc_url
  for RPC endpoint
- dev/scripts/dev_heartbeat.py: Use AITBC_LOCAL_RPC and AITBC_GENESIS_RPC
  env vars for RPC URLs
- cli/aitbc_cli.py: Use AITBC_FOLLOWER_HOST and AITBC_FOLLOWER_PORT
  env vars for network peer display

This makes the codebase more portable and configurable for different
deployment environments.

dev/scripts/dev_heartbeat.py

@@ -14,8 +14,8 @@ REPO_ROOT = Path("/opt/aitbc")
 LOGS_DIR = REPO_ROOT / "logs"
 
 # AITBC blockchain config
-LOCAL_RPC = "http://localhost:8006"
-GENESIS_RPC = "http://10.1.223.93:8006"
+LOCAL_RPC = os.getenv("AITBC_LOCAL_RPC", "http://localhost:8006")
+GENESIS_RPC = os.getenv("AITBC_GENESIS_RPC", "http://localhost:8006")
 MAX_HEIGHT_DIFF = 10  # acceptable block height difference between nodes
 
 def sh(cmd, cwd=REPO_ROOT):