[docs] Add documentation for the new Distributed Scheduler module

[ramonfigueiredo]

Describe the enhancement Add documentation for the new Distributed Scheduler, a standalone Rust module that offloads frame dispatching workload from Cuebot to enable horizontal scalability for larger render farms.

The documentation should include:

1. Getting Started Guide (docs/_docs/getting-started/deploying-scheduler.md)

2. Technical Reference (docs/_docs/reference/scheduler.md)

3. News/Release Announcement (docs/news/2025-12-12-distributed-scheduler-release.md)

4. README updates

• docs/README.md
• rust/README.md