Improve course capstone workflow

[jules-tth]

Scope

• Expands docs/course/capstone.md from a short checklist into a practical operator workflow.
• Adds lab safety constraints, suggested stacks, phased build/security/monitoring/failure-drill steps, a handoff template, and completion checks.

Verification

• python -m pip install -r requirements.txt could not run because python is not on PATH.
• python3 -m pip install -r requirements.txt passed.
• python3 -m mkdocs build --strict passed.
• make build passed.
• git diff --check passed.
• find docs -type f -name "*.md" -size 0 -print returned no files.

Duplicate-prevention

• Checked open PRs from jules-tth; no open PR touches docs/course/capstone.md.

[jules-tth]

Reviewer assignment to bdorlus failed during PR creation: GraphQL: jules-tth does not have the correct permissions to execute RequestReviewsByLogin (requestReviewsByLogin).