fix: txn-bot port 43069 not published to host (#899)

Add ports mapping 127.0.0.1:43069:43069 to txn-bot service in
docker-compose.yml, matching the pattern used by ponder. Add txnBot
status URL to ENVIRONMENT.md Common URLs section for consistency.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/ENVIRONMENT.md

@@ -118,6 +118,7 @@ docker inspect landing --format '{{.NetworkSettings.Networks.harb_harb-network.I
 - **Staking app:** `http://localhost:5173/app/`
 - **Ponder GraphQL:** `http://localhost:42069/graphql`
 - **Anvil RPC:** `http://localhost:8545`
+- **txnBot status:** `http://localhost:43069/status`
 
 ## Resource Notes