Make webserver config.py location customizable

Make webserver config.py location customizable: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). Use case / motivation Since AIRFLOW HOME/config is already in PYTHONPATH (though that's also hard-coded), it's common for user to mount all config files under AIRFLOW…

The task

**Use case / motivation** Since `AIRFLOW_HOME/config` is already in `PYTHONPATH` (though that's also hard-coded), it's common for user to mount all config files under `AIRFLOW_HOME/config`. However, this `webserver_config.py` needs extra handling, either by mounting using a `subPath` explicitly, or in my case,…

Part of FineEnvs/MiMo-V2.6-RL-harbor-code.