feat(lab2): Threagile baseline and secure variant analysis

[RII6]

Goal

Generate a STRIDE-based threat model of OWASP Juice Shop using Threagile, create a hardened architectural variant, and compare the risk reports.

Changes

• Added submissions/lab2.md containing the baseline risk table, top-5 risks with STRIDE mapping, and trust boundary observations.
• Created labs/lab2/threagile-model-secure.yaml to include architectural mitigations (enforced HTTPS, DB encryption at rest, declared prepared statements, and removed insecure log storage).
• Added a risk diff analysis comparing the baseline and secure variant outputs.

Testing

• Ran the threagile/threagile:0.9.1 Docker container locally against both the baseline and secure YAML models, and successfully verified the generated risks.json outputs to calculate the risk diff.

Artifacts & Screenshots

• submissions/lab2.md
• labs/lab2/threagile-model-secure.yaml

Checklist

• Title is clear (feat(labN): style)
• No secrets/large temp files committed
• Submission file at submissions/labN.md exists