docs: clarify thermal-fin MLOps mini-project

[prudhomm]

Summary

• clarify the 3D four-fin thermal-fin mini-project and its physical interpretation
• document the parameter-to-response mapping mu=(L,t,Bi) and S(mu)=Tbar_base(mu)
• describe the end-to-end local/Gaya workflow, train/validation/test split, and surrogate-based optimization
• add 3D mesh and temperature visualization figures with explanations

Validation

• git diff --cached --check
• asciidoctor -o /dev/null docs/course/modules/m2/pages/session2-thermal-fin.adoc
• asciidoctor -o /dev/null docs/course/modules/m2/pages/mlops/project.adoc
• asciidoctor -o /dev/null docs/course/modules/m2/pages/mlops/lifecycle.adoc
• Antora generation completed page generation; final repository post-check exits non-zero on existing unrelated repository checks.