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>

docker-compose.yml

@@ -190,6 +190,8 @@ services:
       - GIT_BRANCH=${GIT_BRANCH:-}
     expose:
       - "43069"
+    ports:
+      - "127.0.0.1:43069:43069"
     restart: unless-stopped
     networks:
       - harb-network