fix: declare SOAR dotenv dependency

[Haihan-Jiang]

The SecOps SOAR package imports dotenv from secops_soar_mcp.bindings, but python-dotenv is not listed in the package dependencies.

This adds the missing runtime dependency to server/secops-soar/pyproject.toml.

Tests:

• python3 -m py_compile server/secops-soar/secops_soar_mcp/bindings.py
• python3 -m pip install --dry-run ./server/secops-soar (metadata prepared; dependency resolution then stopped because the local Python is 3.9 and the existing mcp>=1.4.1 requirement needs Python 3.10+)
• git diff --check

[Haihan-Jiang]

This is ready for review. The SOAR dotenv dependency is now declared, and the visible checks are green.