[c7#151] Extend lock timeouts

> Synced from https://github.com/bpm-crafters/process-engine-adapters-camunda-7/issues/151

Library version: 2025.08.3

### Scenario
For the remote adapter we want fairly low lock timeouts, preferably around 1 to 5 minutes, because: Why would you need more for fast executions? However, all external tasks are fetched in batch, i.e., distinguishing lock timeouts per topic (thus depending on the expected load) is not possible. It would be nice to have if the adapter were to extend locks automatically.

### Current Behaviour
Lock timeouts are not extended.

### Wanted Behaviour
A scheduled task at the rate of half the lock timeout which detects currently running external tasks and extends lock timeouts as needed.

Start in the remote adapter's batch external-task fetching and lock-timeout handling. Confirm the scheduled check runs at half the configured timeout, identifies running tasks, and extends their locks as needed; done means long-running tasks do not lose their locks.

Written by the indexing model from the issue text.