docs: add backend worker scaling governance policy

[Gentle842]

Overview

This PR closes a governance gap by documenting the backend background-worker scaling policy. It adds Governance/backend/WORKER_SCALING.md as a versioned reference for how workers scale and how backpressure is handled, and links it from Governance/README.md so contributors and maintainers can find it.

Related Issue

Changes

📄 Governance Documentation

• [ADD] Governance/backend/WORKER_SCALING.md

  • Documents the backend background-worker scaling policy.
  • States how workers scale and how backpressure is handled.
  • Defines ownership and the review/update cadence for this document.

• [MODIFY] Governance/README.md

  • Links to the new backend/WORKER_SCALING.md document.

Verification Results

Scope check:
✅ Changes limited to 2 files
✅ All changes contained within the Governance/ folder
✅ No code paths modified — no regression risk to existing functionality

Acceptance Criteria	Status
Governance requirement is implemented successfully	✅ Governance/backend/WORKER_SCALING.md added
Scope is limited to a maximum of two files	✅ 2 files changed
No changes are made outside the Governance folder	✅ Only Governance/ paths modified
No regression in existing functionality	✅ Documentation-only change
Tests pass and code follows project standards	✅ No code or tests affected
Change is documented	✅ Policy documented and linked from Governance/README.md

Closes #2772

[drips-wave]

@Gentle842 Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits

[RUKAYAT-CODER]

Thank you for contributing to the project